When you're prepping for the SAT or ACT, one of the best things you can do to improve your score is work on practice math problems. Kaplan is now providing a free tool for getting ACT or SAT practice problems online. Kaplan's SAT Quizbank and ACT Quizbank allow students to get practice test problems with a lot of flexibility.
Signing up for a free account on the Kaplan website will allow you the log in to the Quizbank. You'll be presented with a variety of options. You can take choose between timed and untimed practice tests, adjust the difficulty of questions, and choose to take a test that includes all of the subjects you'd see on the SAT or ACT, or just focus in on single area like math.
Once you've completed your practice test, you'll get immediate results. You can walk through the questions you missed one at a time, viewing worked out solutions so you can improve for next time. As you take more practice tests, you should start to be able to get an idea where you need more practice because your results section will show you what types of questions you are missing (algebra, geometry, other), how long you spent on each question in seconds, and the difficulty of the problem. As you create new practice tests, you can then tweak the options to focus in on the areas where you need practice.
The quizbank has a large supply of questions, around 500 math questions,so you'll have no problems letting it keep you busy for a long time. As far as free ACT and SAT practice tests go, Kaplan's Quizbank is top-notch. For more on Kaplan, check out my article on Kaplan's online math SAT and ACT prep.