The best study guides are
those provided by the test
makers themselves. For the
SAT, nothing beats the College
Board's "Official SAT Study Guide."
The College Board has
recently released the 2nd
edition of the "Official
SAT Study Guide." The
latest edition contains 10
practice tests!
For the ACT, "The Real ACT Prep Guide," is great because it contains 3 real ACT tests and provides the answers and explanations to all the test questions.