I am posting this link in both places - Books and College Bound/College kids because it's so freaking cool.
Kaplan, the test prep company, is offering 130 of their test prep books for free on Kindle, Ipad, and Nook for the next couple of days.
All you have to do is go to this link and read about it and see the titles. I use Amazon and have the reader for my Kindle as well as for my home computer.
Even if you don't have an ereader, you can participate. Just download the app for the respective company (Amazon, Barnes and Noble or Apple applications for the device) and then go to search by title in the ereader bookstore. For me, I searched on Amazon for "Kaplan". All those titles that are listed at $0.00 qualify.
There is something for everyone here and books that aren't even specifically for testing. I found some fascinating titles, actually.