Popup is an interactive learning aid for pairs of words. It behaves much like
a stack of flashcards, but handles one-to-many and many-to-one word
relationships better, and includes an integrated scheduler for efficient use
of your 'cards'. Popup was written by Bjorn Ghola and Rob Burns.
Features:

* An editor for cardstack files with support for copying and pasting groups
  of words, as well as drag and drop.
* Three quiz styles: multiple choice, spelling, and flashcard.
* Supports quizes and practice
* Graduated time interval scheduler.
* Localized for Thai and German.

LICENSE: GPL2 or later

WWW: http://popup.sourceforge.net/