ACT

ACT:A good source for ACT testing info with online registration.
http://www.act.org/

Princeton Review offers a broad array of education resources, including “Word-a-Day,” vocabulary practice.
http://www.review.com/

SAT

College Board
http://www.collegeboard.org/sat/html/students/indx001.html

College Board Online
http://www.collegeboard.org/

PSAT

PSAT/NMSQT: Preliminary SAT/National Merit Scholarship Qualifying Test
http://www.collegeboard.com/student/testing/psat/about.html