Study Island: An online teaching and tutoring system for all courses and levels. Try it for free.

 

Khan Academy: Make a FREE account with your Gmail account and get studying! This tool is great for all subjects, but especially math and test prep

 

SAT Prep: This takes you to the College Board website, which is the best resource for SAT prep since they made the test. 

 

ACT Prep: This is the official website for the ACT Test and includes important information, dates, and practice test questions.