College Board - information about registering and preparing for the SAT
FreeSAT1prep.com - SAT Test Preparation Tips - The most useful sections of the site can be accessed in the top menu: Preparation Advice, SAT Score, SAT Test Structure, Test Day Tips, Critical Reading Section, Math Section, Writing Section.
High School Ace - This has an SAT Question of the day, College Prep related links under Guidance, and many other links to help with high school level course work.
Practice Tests and Questions
Kaplan Test Prep - You need to register to use their free SAT QuizBank. Click View Demo in left menu to learn more. (There are lots of ads for their test prep products.)
Number2.com - You need to register to use this free test prep site. Also, click on SAT and get a Word of the Day and Question of the Day.
4Tests.com - This has free practice math and critical reading questions. However, you may find some of the blinking graphics distracting.
SAT Preparation - This has quizzes with over 3500 questions.
Free SAT Essay Prep - He has some very good information on preparing for the essay. Also check his Valuable Links at the bottom of the page for more SAT prep sites.
Vocabulary University - Top SAT* Words - This is a collection of puzzles to help you practice vocabulary words.
5000 Free SAT Vocabulary Words - This gives words and definitions.