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 allows you to train the entries you study and let you follow your progression in remembering them. Finally, it makes it easy to review entries you did not remember by reviewing them on screen or printing them on a small booklet.
Tagaini Jisho is also one of the rare (if not only) free software to feature complete stroke order animations for more than 6000 kanjis.