If you use emacs org-mode, check out org-drill http://orgmode.org/worg/org-contrib/org-drill.html. It uses the same algorithms, allows you to tweak everything, and you can keep your flashcards alongside the relevant notes/code/files/issues/ToDos/bookmarks/contacts/feeds/calendar-entry/emails/thesis/spreadsheets/journals/diagrams/pictures/evernotes/etc. http://www.youtube.com/watch?v=1-dUkyn_fZA, rather than in a totally separate program.