Yesterday Apple approved Flashboard, the free (ad-supported) version of Cardboard. You can use it to study flash cards on your iPad. One of the features I like most is that you can create and manage your sets of flash cards from Google Docs. The app can easily import your set and bring it to life.
You can also browse Quizlet.com for sets; they have an amazing collection of cards from students like you.
I'm using Apple's iAd within the app. This comes shortly after my AdMob account was disabled for no apparent reason.
I was happy to see it hop up to #37 on the charts this morning - it means people are studying! I've heard from some teachers in the past and I hope those schools fortunate enough to have iPads can use it as one of many tools to make learning fun.