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

ACT:
http://www.act.org/

TestPrep:
http://www.testprep.com/wwmain.sat.html

GoCollege:
http://www.gocollege.com/api/eliasup.exe/gocollege/

Kaplan:
http://www1.kaplan.com/view/article/0,1898,1626,00.html#REGISTER

SAT/ACT:
Optional Schools http://fairtest.org/optional.htm

College Board Essay Prep:
http://cbweb6.collegeboard.org/writewellCB/html/essintro.html

Princeton Review:
http://tester.review.com/