Parley supports many language specific features but can be used for other learning tasks just as well. It uses the spaced repetition learning method, also known as flash cards.
Features:
Different test types
Fast test setup with all options in one dialog
More than two languages
Find words (also by word type) quickly
Easy lesson management
Premade vocabulary files ready to use
Share and download vocabulary using Get Hot New Stuff
Open XML file format that can be edited by hand and is easily usable with scripts