Brain Flips is a relatively new flashcard service. Brain Flips allows anyone to create and share flashcards about any topic. To create flashcards you must register (it's free), but to just use the publicly shared flashcards does not require registration.
What makes Brain Flips unique is that it offers three ways to review the flashcards. The three modes for using the flashcards are introduction mode, traditional mode, and response mode. In the introduction mode the flashcard's question and answer appear side by side. In traditional mode the flashcards display the question on one side and displays the answer on the other side when clicked. In response mode the user is prompted to put in an answer before the correct answer is displayed.
Applications for Education
Brain Flips is a nice, free, option for students to create flashcards and study them. Brain Flips is interesting because it does offer the graduated modes of studying.
Here are a couple of related items that may be of interest to you:
10 Places to Make and Find Flashcards Online
Free World U - Free K-12 Flashcards