Cabra is an easy, effective, cross-platform, award-winning, and - above all - FREE studying tool. Anyone from kids to students to grandparents can learn math, languages, history, and more using Cabra!
Why is it so great?
Unlike the other flashcard programs you see out there, Cabra is under active development and always trying to improve. Feel free to contact me.
The .exe installer works for Windows only, but the .jar installer works on any OS with a Java Virtual Machine (read: anything.) Windows users should choose the .exe installer, but if you choose the .jar installer it's OK as well.
If you just want to try out Cabra (you don't want to install it), just download the standalone JAR.
Cabra works for flash drives too, just download Cabra portable and save it to your flash drive. You can then run it from your flash drive.
Source is available, and it's in zipped form (.7z). Post on the forums if you need it in another form.