khanacademy.org : This site provides excellent tutorials in math and other subjects. The author of the tutorials solves problems using techniques almost identical with mine. In addition, it provides superior tutorials for the SAT which will also assist on the ACT.
collegeboard.org : This site is authored by the makers of the SAT and provides excellent resources for preparing for the SAT/PSAT, college searches, scholarship searches, and many other topics for the college bound student. This is also the site to signup to take the SAT.
act.org : This sites provides some free tutorials for the ACT and links to purchase guides for the ACT.
desmos.com : This site provides free on-line calculators that allow students to explore relationships in math.