http://www.funnelbrain.com/
This is a student-driven academic question-and-answer community where students create and share multimedia flashcards. Students can add a third side to any flashcard to explain a difficult concept or to share a favorite mnemonic device. They can also include videos, photos, voice recordings and math equations. FunnelBrain users can then share their questions—and collaborate on creating complete sets of flashcards on any topic of interest—with classmates and other students around the world.