The College Board website offers practice tests and questions with answers. Sample questions, study guides and a full practice test are available on the site for free.
The College Board is the creator of the SAT and publishes many helpful materials on its website. The free practice test that is online comes complete with a scoring guide that provides answers for all sections of the SAT. The website also offers a "question of the day" portion that provides the answer and an explanation. Specific sections of the test can be practiced, and answers are provided after the question is answered.