Other
Graduate Educational Information Service: Test Prep Review
Contains great information to help students prepare for many national standardized tests, including the SAT, PSAT, ACT, GED, and many others. Along with tips and strategies, there are a number of free practice tests.
Khan Academy
Khan Academy: Test Prep
A collection of links to test prep materials; NCLEX-RN if for nursing students and has advanced human biology materials; IIT JEE has trigonometry materials.