General

Kanji-Step - Japanese Language Resource Center
This site provides a straightforward, easy-to-follow method for mastering Japanese as a written language. Starting from the basics, Kanji-Step provides  animated images of the Japanese syllabic systems, hiragana and katakana, as well as 100 kanji for more advanced readers. Also featured are  weekly tests similar to the Japanese Proficiency Test, a pen-pal service, cultural information, and more.
http://www.kanjistep.com/index.html

The Japanese Page
This lighthearted site covers a broad spectrum of topics- everything from basic grammar and the writing systems to cultural notes and animal noises in Japanese. The grammar explanations are easy to follow, the list of kanji is extensive, and wav files are included for listening practice. Some of this site's more unique features include the "Henna Nihongo" dictionary of interesting phrases, a guide to Japanese onomatopoeia, and a variety of "fun" Japanese.
http://www.thejapanesepage.com

Japanese-Online
This site aims to teach Japanese through a series of dialogues, written in romanized letters. While this format may not boost a student's Japanese reading ability, it does provide a simple way to learn some basic vocabulary and grammatical concepts. In addition to the lessons, there is an online dictionary, a message board where you can exchange questions and answers with fellow Japanese enthusiasts, and an online store offering a wide selection of Japanese language software.
http://www.japanese-online.com

Nihongo Web: Online Japanese Language Course
An online course from the University of Alabama, aimed at students of Japanese who wish to learn independently. For a fee of $25.00, you can actually get college credit, but before you sign up, the site offers a free-of-charge "preview" so you can see if the learning style is right for you. The course covers all aspects of the language. Reading, writing, and listening assignments are available on the web page, and the university offers a toll-free tutorial line for speaking practice. They will even pair you up with other students online to work on group activities. Interesting!
http://www.ccet.ua.edu/nihongoweb/

Chiron's Survival Japanese
This site introduces the basics of everything: reading, writing, speaking, listening and grammar. The webmaster provides short romanized dialogues, with certain phrases accompanied by helpful sound files. Often, a word in each sentence will be linked to an in-depth grammatical explanation. The sheer volume of information provided could be confusing to the the more casual student or traveler, so I'd recommend this site for a person who already has at least a little familiarity with Japanese, and an interest in developing their skills further.- i.e. learning how to construct proper sentences, or polishing up their pronunciation.
http://www.asahi-net.or.jp/~if2n-szk/jcont.html

 

Reading/Writing

Chipchat Japanese Training
No need for flash cards- test your hiragana and katakana recognition skills through this Java based site. The timed drills display a kana character, and you simply click on the romanized equivalent below. Terrific, convenient reading practice for beginners!
http://www.chipchat.com/NihonGo/

The Japanese Writing Tutor
Utilizing excellent, easy-to-follow animated graphics, this site demonstrates the correct stroke order to use when writing hiragana, katakana, and kanji. The moving images are particularly valuable for getting familiar with kanji, which can often be confusing due to the sheer amount of strokes involved. For many people, written Japanese is the most intimidating aspect of the language, but if this site will help you build a strong foundation in using the proper stroke order, so you'll be able to tackle even the most complex kanji.
http://members.aol.com/writejapan/

Kanji Names Project
This unique project is a collection of Japanese names and their meanings. A group of students submitted a explanations of the kanji used to write their names, sometimes accompanied by their personal reflections on their names. The characters for each person's name are displayed in graphical format alongside their explanations, for reference. After learning about the kanji for Japanese names, one may wish to write their own name in kanji, so this site also provides a link to a book which will teach you how to do just that.
http://www2.gol.com/users/billp/students/kanjiname/

English/Japanese Flash Cards
This simple site operates as an online flash card quiz... the page displays a phrase, and you try to translate it, then click the "answer" button to see if you were right. Simple and fun! The words and phrases seem to be rather colloquial, so this site may be of interest primarily to those who have studied Japanese for a few years already, and are seeking to expand their casual vocabulary. 
http://www.schei.com/cgi-bin/flash.cgi

Randomly Chosen Japanese Words
Another learning tool in a flash card format, this site randomly generates twenty commonly-used Japanese words in kanji and kana. The readings and English translations are hidden in drop-down menus below each word, making it convenient to test yourself and check your answers. This site is aimed at intermediate-level learners and is particularly good for practicing kanji compounds.
http://www.manythings.org/c/r2.cgi/edict

 

Listening/Speaking

Japanese Listening Comprehension Exercises
The dialogues on this site are likely too challenging for the absolute beginner, but will be just perfect for someone who's been studying Japanese for about a year. Each dialogue is accompanied by a charming illustration, and followed by questions about the content. You can even submit your email address to get your results mailed to you!
http://web.uvic.ca/hrd/japanese/listen/

Listen and Spell
A fun way to test both listening and katakana comprehension, this Flash-based game is perfect for beginners. A voice dictates the names of sea creatures in Japanese, and the player spells the words using the katakana buttons on the screen. You can choose the pace at which you play the game ("Fast," "Faster," or "Furious"), depending on your comfort level.
http://www.manythings.org/wbg/9101s.html

 

Resources for Learning

   Textbooks

Japanese Textbook Discussion Board
Interested in buying a Japanese textbook but aren't sure which one is right for you? Teachers  at this site share their opinions on many textbooks for all levels, making your decision a little easier. 
http://www.japaneseteaching.org/projects/textbook/

    Computer Related

Shodouka
This handy web-based tool allows you to view Japanese websites in Japanese even if you don't have Japanese-language software installed! It requires no downloading- simply type in the URL of a website you'd like to view, and the Page Viewer will display all the text on that page as it's supposed to appear, in kana and kanji. Even the correct text colours show up! It's great.
http://www.lfw.org/shodouka/

Japanese Software and Information
The generous webmaster of this site provides a free, downloadable Japanese word processing program as well as other educational tools. Convenient... and you can't beat the price!
http://www.physics.ucla.edu/~grosenth/j_main.html

Welcome to AsiaSoft
For those who are willing to invest some money into Japanese software, AsiaSoft offers a wide variety of programs, from simple word processing to website building software. 
http://www.asiasoft.com/english/index.html

   Organizations

The Japan Foundation
An organization devoted to promoting understanding of the Japanese language and cultural exchange. The site provides listings of local branches of the foundation, academic publications, information on the Japanese Proficiency Test, and more.
http://www.jpf.go.jp/

Japan Association of Translators
If you are a Japanese translator, or need one, this is the place to go. For those in need of translation services, the site provides a directory of Japanese-English translators. For those involved in the profession, there is information about joining the organization, as well as an extensive collection of helpful articles about being a translator in Japan. 
http://www.jat.org

   Online Dictionaries

Jim Breen's WWWJDIC
In addition to performing typical online dictionary functions, this site is unique in that you can copy text from a Japanese website or document, paste it, and the dictionary server will translate the basic vocabulary in the sentence. This, of course, leaves you responsible for translating the grammar... but it's an extraordinary resource for overcoming more obscure words. Very convenient when you're surfing the web for Japanese reading practice.
http://www.csse.monash.edu.au/~jwb/wwwjdic.html

Kanjidict
This dictionary is easy to use and offers a variety of advanced features. You can limit or expand your search to specific categories, such as law terms, financial terms, and proper names. In addition to providing English-Japanese and Japanese-English translation, kanji and kana are shown for each word. The definitions are linked to synonyms, allowing you to expand your vocabulary, and you can also click on the kanji provided for more information and a list of similar characters.
http://kanjidict.stc.cx/dict

   Linguistics

Japanese (The Languages of the World by Computer and the Internet)
This simple page provides a linguistic overview of Japanese, an explanation of how to write in Japanese using a computer, contact information for retailers who carry Japanese word processing products, and other miscellaneous information. Most worthy of note, there is a detailed section on various dialects on Japan, and information about the origins of the language. 
http://www.threeweb.ad.jp/logos/japanese.html

Studies in Japanese Linguistics
For the serious student of Japanese linguistics, this site provides thorough reviews of several books on the subject. Also included are the books' ISBN numbers, to facilitate finding and purchasing of the texts.  
http://csli-publications.stanford.edu/site/SJL.html

Alternative sci.lang.japan FAQ
This extremely thorough list of questions and answers is an an incredibly informative resource, covering every aspect of the Japanese language, from vocabulary to syntax to the historical origins of words and phrases. 
http://www.csse.monash.edu.au/~jwb/afaq/afaq.html

 

Japanese for Travelers

Nihongo Ryokousha no Tame no
This page's title translates simply to "Japanese for Travelers," and indeed, the site provides an easy resource for travelers to get a grasp on some basic words and phrases that may prove useful in their journey. There are several categories to choose from, such as Basic Words, Numbers, and Shopping/Dining,  and sound files are provided for each word in a given category. There are also short quizzes available, to test what you've learned, and quite a few useful links to other sites dealing with topics in Japanese travel. 
http://www.travlang.com/languages/cgi-bin/langchoice.cgi?lang1=english&lang2=japanese&page=main

Survival Japanese
A practical overview of common words and phrases, this easily-navigable site offers audio samples and attractive PDFs that can be printed as pocket-sized references. The site's only drawback is that it features romaji only, without any accompanying examples in Japanese text.
http://www.ajalt.org/sj

Sushi Vocabulary
Just what every hungry traveler in Japan needs- a quick list of sushi terms! Print this one out and use it as a handy reference on your trip- or use it to impress the chef in your favourite local sushi bar. 
http://www.bento.com/sushivoc.html

Casual Speech and Dialects

Japanese slangs you won't find in a dictionary
If you're hoping to move beyond that formal, textbook-style Japanese, this brief but informative page will supply you with some fun phrases for use outside the office or classroom. Learning slang will allow you to develop a more natural pattern of speech, as well as aid your comprehension skills when you're watching Japanese TV or movies.
http://japan-cc.com/slang.htm

Japanese Slang for Peter
It's not clear who Peter is, but anyone will be bound to enjoy this thorough look at commonly used slang and casual words. Admittedly, some of the terms introduced are not exactly slang (i.e. kabuki) but nevertheless, the explanations provided for each term are definitely worthwhile reading. The knowledge gained from this site can certainly put some "oomph" into your Japanese vocabulary. 
http://www.geocities.co.jp/SweetHome/2852/English/slang-e.htm

Try to learn the Kyoto dialect
Another great site about Kansai-ben, this site focuses on the dialect specific to Kyoto. It's more refined than Osaka-ben, but equally fun to learn. If you ever wanted to try speaking like a geisha, here's your chance!
http://www.kyoto-np.co.jp/kp/ojikoji/kotoba/kotoba_e.html

How to Speak Nagoya Dialect
Sample sentences written in both Japanese characters and romaji help illustrate the use of common regionalisms from the Nagoya area, located south-west of Tokyo. Each phrase is accompanied by the standard Japanese version for contrast.
http://mediazone.tcp-net.ad.jp/MISO/EBITENW/NB

 

Articles

Manifestations of Gender Distinction in the Japanese Language, by Alexander Schonfeld
This informative article analyzes the way in which written and spoken Japanese differentiate between the sexes. The author provides clear explanations of the various forms of the words "I" and "you" as used by men and women, the levels of politeness and how they are used in Japanese society, and examples of the ways in which men's speech differs from women's speech. Extremely useful for those who wish to speak naturally according to their gender.
http://www.coolest.com/jpfm.htm

Remember...? by Stephen Trussel
The expressiveness of the Japanese adjective "natsukashii," as opposed to its English near-equivalent, "nostalgic," is discussed in this thoughtful article. The author touches upon the interesting question of why native speakers of English sometimes prefer to use a Japanese word to communicate a feeling or idea. He uses short anecdotes to illustrate his points, and supports his opinions with linguistic analysis. 
http://www.trussel.com/jap/remember.htm

Strategies for Effective Study of Foreign Languages: Learning Japanese
This paper explores the general principles of language learning and applies them to the study of Japanese. The author provides an overview of several practical strategies for learning a foreign language, including memorization, putting together known elements in new ways, guessing meaning from context, and thinking positively.
http://www.tci.ac.jp/~naphtali/SenseiOnline/EffectiveStrategies.htm