Free practice test bank
Varsity Tutors has created a massive FREE practice test bank for all kinds of standardized tests, including SAT, SSAT, ISEE, GED, GMAT, HSPT, CLEP, AP, ACT, and ACCUPLACER -- and also generic subjects such as algebra 1, geometry, or calculus. It contains tens of thousands of practice problems.
You can also create a free account so you can save your test results and keep track of progress over time, as well as create your own tests.
Note: this is not for math only but includes English, science, reading, writing, social studies and so on -- whatever subjects are tested in any particular test.