Japanese/Software

Learning Japanese

Tagaini Jisho is a free, open-source Japanese dictionary and kanji lookup tool that is available for Windows, MacOS X and Linux. Features complete stroke order animations; lets you train entries you are studying and follows your progression. Released under the GPLv3.
JFC Japanese flashcard program. Can be used to drill user-created wordlists. Complements JWPce well.
JFC for Mac OS X Mac version of Japanese flashcard program. It seems quite undeveloped.
PyJflash is both a Japanese flashcard viewer and a spreadsheet-like conversion utility and editor supporting various formats for Windows, Linux and Unix-like OSes. (no longer being maintained)
Rikaichan, a pop-up Japanese-English/German/French/Russian dictionary extension for Firefox. It's simple to use, all you have to do is just hover the mouse on top of a Japanese word. It even automatically de-inflects verbs and adjectives, which is useful.
jMemorize is flash card software that has some Japanese flash cards made already.

Learn Japanese the fun way | Nihongoup Japanese educational game and reviewing tool.
Stackz! Flashcard type program that lets you drill custom wordlists. Good selection of downloadable wordlists.
Kanji Sketch Pad Draw kanji with your mouse and get coached on where you went wrong. Built in information on usage and readings. Automatic revision scheduler based on performance.

Coscom Kanji learning software
Popup Japanese Dictionary for Windows, a Japanese dictionary for Windows which allows the looking up of words by copying them to the clipboard. The meaning of the word will be displayed in a popup window. Features include lookup history and export to Anki capability.

gjiten, by Botond Botyanszki, is a Japanese/English/kanji dictionary for GNOME that uses Jim Breen's EDICT and KANJIDIC files.
JWPce, by Glenn Rosenthal, is a Japanese word processor for Windows, including a Windows CE version, that's released under the GPL. It includes EDICT dictionaries, kanji information, etc.
Moji is an extension for Mozilla Firefox that can look up words and kanji while you browse. It's released under the GPL.
PAdict, by Lars Grunewaldt, offers EDICT-based dictionary lookup on the Palm OS without additional libraries. It's released under the GPL.

JED, a dictionary application for Android, includes stroke order, searching by radicals, romaji and different codes and working with clipboard.

JEDict is a dictionary program that uses EDICT files to look up kanji. It provides readings, definitions, and radicals. The free version can look up kanji in a basic dictionary, but the registered version ($25) supports additional specialized dictionaries. Only available for Mac OS X.
NJStar Communicator/Word Processor Text Processor for Windows, gives the ability to write kanji in ani text input, selecting them with different input methods
KanjiQuick is a dictionary program with all data from Spahn/Hadamitzky's Japanese-English Kanji Dictionary (has a Japanese-German version too). It comes with a free EDICT reader, a translation and a TTS- (Text To Speech) module. It can be evaluated for free (MS Windows only).

kdrill, by Philip Brown, is an interactive, intuitive kanji learning program, which is highly scalable to the level of the learner.
by Filip Kábrt is the hybrid of learning tool and a dictionary for Chinese and Japanese, supports a lot of dictionary formats including EDICT, supports flash cards, works under Windows.
kanatest is a flashcard-like program for learning the kana (hiragana, katakana), available for Linux under GPL.
JKana test is a Java version of kanatest.

KanjiGym Light is a free study aid for the Kanji learning system by James W. Heisig. Available in English, German, French and Spanish for Java and Palm OS.
Kotoba! is a free multilingual Japanese dictionary for iPhone and iPod touch devices.
Project LRNJ is a role-playing game for Linux, Mac OS X, and Windows that teaches hiragana, katakana, kanji, and some English loan-words. The site also includes a "phrase of the day" in Japanese, which expands from normal writing, progressing from including kanji, to pure hiragana, to katakana, to romaji, to a literal translation, to a sentence with correct English grammar. (warning: some of the character combinations being taught are rather unnatural, like ッマ, and the software is not currently being maintained)
Sokushuji App for learning Kanji on the iPhone
Obenkyo is the App to learn Kanji on Android, with different test types (includes drawing a kanji), errors highlighting

iKana is a hiragana and katakana study tool for the Mac by ThinkMac Software. It features flash cards, a speed recognition test and a word romanisation test. Only available for Mac OS X.
iKanji is a kanji study tool for the Mac by ThinkMac Software. It features flash cards, a kanji meaning test, kanji readings test and kanji stroke order test. It covers all kanji in Japanese school grades 1 to 6 and JLPT levels 1 to 4. Only available for Mac OS X.

For information about Windows and Macintosh operating systems see: the Penn State site on Working with Japanese.
For *nix systems, you're probably best off with uim or SCIM. See uim for Wikibooks documentation on the former.

Jim Breen's site also has a comprehensive list of free and non-free software.