In this short posting, I'd like to point out two sites where you can make flashcards and an app which is fun to have on your mobile.
Cramberry and Braineos are two free flashcard sites where you can create, study and even challenge your friends with vocabulary. Although they are great for learning languages, you can use them to revise almost any subject you want to and share with your friends.
And for fun, why not explore Save the Words where you can learn all kinds of new words?
SnaPanda is an app which you can download to your mobile. Easy and handy to use whenever you want to.