The College Board (www.collegeboard.org):
This is the site for SAT on-line registration. There is a lot of helpful information about the tests (SAT I and II, PSAT), when and where they are given, and other services such as SAT Question of the Day, Registration, College Board Test Dates, CSS Financial Aid Profile, College Search Program, Essay Prep On-line Essay Evaluation Service, and Financial Aid Services.

ACT On-line (www.act.org):
The ACT Assessment, or "A-C-T" as it is commonly called, is a national college admission examination that consists of tests in: English, Mathematics, Reading, and Science Reasoning. ACT results are accepted by virtually all U.S. colleges and universities. You can register here, check test dates and test centers, and use other services such as ACT Assessment, College Connector, and Discover Career Planning.