Hesitant to shell out thousands for a test prep service? Try a free, self-directed program online at TestPrepReview.com. The website features over 30 "self-assessment modules" that cover all the areas you'll be tested on in the SAT. From advanced algebra to sentence flow, each module offers students a taste of and feel for the test. Once you're done correcting your own answers, you can note areas that need improvement and proceed to TestPrepReview.com's "self-improvement directory" for basic resources to help you improve your score.

If you want to do some extra vocabulary work, the website has compiled a list of words frequently found on the SAT and GRE. Print out the words and definitions to memorize on your own time. (You can do the same with their handy list of prefixes and suffixes.) 

For more test prep resources, check out the entire Exam Cram archive.