SparkNotes has a really great section that is devoted in SAT and ACT tests. And you know what? All the resources you will find from their site are absolutely free! All you need to do is register to enjoy all the privileges.
The site is giving away free sample tests that allow students to practice and assess their skills. The length of the test may not be as long as the actual ACT or SAT tests but these are good enough to have an idea about taking the exam. Just explore the site and I am sure that you will learn a lot from it. And guess what, the site also has a forum where students can mingle and discuss anything and everything about taking up these tests.