Tagaini Jisho is a free, open-source Japanese dictionary and kanji lookup tool that is available for Windows, MacOS X and Linux and aims at becoming your Japanese study assistant. It allows you to quickly search for entries and mark those that you wish to study, along with tags and personal notes. It also let you train entries you are studying and follows your progression in remembering them. Finally, it makes it easy to review entries you did not remember by listing them on screen or printing them on a small booklet.
Tagaini Jisho also features complete stroke order animations for more than 6000 kanji.

Tagaini Jisho is still in development - although the released versions can be considered as stable and even sometimes useful, many features are still to be added before it reaches a "complete" milestone.
The latest bug-fix release of 0.2.6 is now available:
http://www.tagaini.net/download
It includes the Kana selector fix that was broken in 0.2.6.1 as well as some other improvements including a Czech translation of the GUI.
A bug-fix release of 0.2.6 is available for download. This fixes a couple annoying bugs, including the kana selector always appearing on program startup.
http://www.tagaini.net/download
Edit: release withdrawn as it made things worse than 0.2.6.
A stabilization of the 0.2 series, this release brings improved ordered lists, a new kana selector widget that allows beginners to study kana characters, HTML/Javascript export of entries suitable for doing flashcards on mobile phones, German translation of the user interface, a nicer detailed view, a much improved build system that uses the best of both CMake and CPack, a new icon theme, and many others improvements and fixes. Although minor releases may still occur in this branch, the development effort will be concentrated on the 0.9 series.
A lot of work has also been done in order to improve the build system, with great results so far. Third-party data are now downloaded transparently, the build process is now flawless on both Linux and Mac, and CPack integration makes it easy to produce Mac, Debian or RPM packages from the source code.
Tagaini Jisho 0.2.6 can be downloaded at http://www.tagaini.net/download
A second release candidate for 0.2.6 has been released. Although it was not expected in the first place, many bugs were reported against rc1 and many changes have been performed to the build system, hence this new test version to ensure everything is fine on all platforms. You can download it here:
https://launchpad.net/tagaini-jisho/devel/0.2.6rc2
We are particularly expecting feedback from Mac users since they are the first to experience packages built using CPack, the CMake packaging facility. CPack should make our release manager's lives much easier, but our CPack-built packages need testing. Other platforms are still using the old packaging scripts and are therefore not affected, but we would greatly appreciate if Mac users could report their experience regardless of success or failure on the forum or mailing list. Note that this RC requires OSX 10.6 to work, although we will try to make 0.2.6 compatible with 10.5 at least.
0.2.6 will be released between august 16th and august 20th, so please test this version as much as possible and report your experience. Also please don't hesitate to submit translations of the interface in your language using Qt Linguist and the translation templates you can find here:
http://gitorious.org/tagaini-jisho/tagaini-jisho/trees/master/i18n