OpenCards is a flashcard learning extension for OpenOffice Impress.It is completely free and open-source software.The Lastest version OpenCards 0.16 was released on 23-7-2008.
... is easy to use: Just create flashcards as you're used to create Impress-slides
... is well supported: There are already millions of freely available flashcard-sets
... allows to learn any Impress/Powerpoint-file as flashcard-set without conversion
... runs on every major operating system and is free and OpenSource
... will reduce your memorization efforts by implementing state-of-the-art methods for spaced repetition
OpenCards tutorial (only part 1 :( )