This page has a quick summary of the ASVAB exam.
This page has more detail on the ASVAB test scoring and test areas. There are also links to sample questions.
Here is another page that talks about what to expect on the ASVAB, along with some videos that show testing conditions.
This site goes over the current rules for the SAT and has practice tests for both the multiple choice and free response math questions.
Breaking Down the New SAT
This site has descriptions of the ACT exam, test taking tips, and sample tests.