ExamBusters has been around for some time, offering study cards for a variety of subjects, in printed or electronic formats for Windows PCs. They have ported 25 of their popular CD-ROM-based products to the iPhone, including AA+ Geometry Study Cards shown here. The Study Card templates are nearly the same for each subject matter, and the interface is very easy to use. I did get annoyed after a while by the slow flipping of the cards. Still, these collections of inexpensive electronic flashcards are great as tutorials or a quick course refresher.