Superflashcard is another option in a long list of websites that allow you to create your own flashcards online for the purpose of studying. It has a lot of the same features as some other sites, and although its main focus is generating income, they do allow their educators access to a paid account with more features for free.
The one main difference I have seen so far is the users ability to auto-schedule reviews to optimize and enhance memorization. There is also a feature to allow users to import/export your flashcards with comma delimited text file. There are also games and multiple study modes for users as well. And because it is like other flashcard sites, Superflashcard allows networking and you can search the public database for flashcards that users have already created.