My flashcard site, Quisition, has now been launched. Actually, it's been available for the last week but I wanted to test things out a little before announcing anything publicly.
You can sign up at:
http://www.quisition.com/
As of a couple of days ago, support exists for user-contributed cards, although no bulk import yet. That will come shortly.
Implementing this with Django has been a delight. Like Python in general, using it a combination of productive and fun that makes you just want to come up with more ideas you can develop with it.