There are also commercial books that you can buy new (or used on e-bay) or get from your local library (try inter-library loan if they don't have them on your local library shelf). Although these books are not as good as the AAMC ones, they do help you practice timed exam with material that is very similar to the MCAT. The ones that I used for practice exams (and be warned that some of these are really not very MCAT-like even though they say they are) include
Kaplan MCAT Comprehensive Review
Peterson's Gold Standard
Flowers & Silver MCAT (by TPR)
Baron's How to prepare for the MCAT (piss-poor)
ARCO MCAT Sample Exams
REA MCAT (by far the worst of the bunch)
For sample reading comprehension tests, you can also use test prep books for other tests such as the GRE, LSAT, GMAT, DAT, OAT, VCAT, etc. All of these have some reading comprehension section that is similar to that on the MCAT. Again, buy these new, used on e-bay, or get them from your local library. Doing many reading comprehension passages can help you with speeding up your reading and in mastering the types of questions asked on reading comprehension tests (which are all almost always of the same six or seven types). The reading comprehension portion of the exam is not a knowledge exam at all, but rather a "how well do you take this kind of test" exam, and therefore, practice makes perfect.