Practice makes perfect, especially when it comes to those pesky standardized tests. Every day, the College Board posts a new Official SAT Question to help you practice for the real thing. You can also see how many people responded to the day's question, and how many got it right or wrong. Sign up here to receive the question via email.
You can take a practice test for free at Number2.com, a test-prep site designed by university professors and graduate students. Online tutorials are free but users are required to sign up. Practice tests are available for the SAT, ACT, and the GRE (for graduate school).