I used a Princeton book to study for the GRE's...
I also borrowed a few SAT-II English & Math review books (also from Princeton) from my younger cousin who is still in high school. Yes it seems odd, but it was a great review as well -- these were all words/terms/lessons I REALLY should know... and it helped!
I also did a bunch of mini-essay questions (you can find that sort of 5 minute question on a lot of sites -- SAT,GRE,ACT, etc...) that help you get ready for the short-answer section and analytical writing. It helped me to just do a million of these fairly ridiculous questions that always seem so easy until you actually have to sit down and write half a page on them. This helped me a lot -- and you could do them anywhere - on the T going to work, waiting for an appointment, during a few commercial breaks, etc.
Hope this helps... and DON'T let the weird computer format of the GRE's freak you out