There are some great free resources online, including some automated prep programs! One of the best is "Number2.com." This is an interactive program. The difficulty level of the questions is adjusted to your ability!
Another great free website for SAT math prep is "SAT Math Pro." This site provides audio-visual explanations to select math problems.
Other free websites worth looking into include: "SAT Exam Prep.com," "I Need a Pencil.com," and "Major Tests.com," These sites provide automated test-like questions for the content covererd on the SAT.
Last, but by no means least, is Khan Academy's free auotmated test prep program. In fact, the College Board has partnered with Khan Academy, so this free test prep program includes real test maker practice questions and exams!!
Remember, to make the most of these resources, you really have to be self-motivated!! Also, if your scoring requirements are in excess of 50 - 60 additional points, using these automated test prep programs may not suffice... but, they provide a good starting point!!