Kaplan PCAT book: best overall prep book. If I only had one book to buy this would be it. Great on Bio, weak on Orgo and okay in math, verbal and reading comp. Good pointers for how to write your essay.
MCAT AudioOsmosis: Overkill for PCAT prep. However, I just popped the CDs in my CD player and listened to them as I drove from home to school and back. Great review of key terms and concepts. Attempts to be funny to keep you entertained and engaged, mostly just annoying. Worth getting if you can afford it.
McGraw Hill: no better than Kaplan for all sections except verbal. If you struggle with verbal, McGraw Hill book has multiple pages of word roots to memorize that I think would be very beneficial.
Schaum's Outlines for College Algebra / Precalculus (2 separate books). Great books for those struggling withcompleting the math section. June PCAT, had to guess on 25% of the questions b/c I ran out of time. I spent about 75 hours working a ton of problems in these two books and I completed the math section with a couple minutes to spare. Moved up from a 62 to a 91% in this section because of these books.
Cliffnotes 5 PCAT Practice Tests: Riddled with errors. Reading comprehension passages were painful to read they were that bad. I would not recommend unless you just want to get some practice on test taking. Do NOT trust the answers.
Dr. Collins : As I mentioned, I bought this second hand. Perhaps it was not the most up to date version. The math section included stuff on trig and geometry which is no longer on the pcat. The bio section was helpful but not as indepth as Kaplan. Chem was a good review. Verbal mostly just practice tests. Same with reading comprehension. I liked Dr. Collins b/c it was more concise than some of the other resources but also had a good number of practice tests for each section (most had 8 practice tests). Would not spend the full price of $300 for it. However, the used priced I paid of $150 was worth it. Plus there is sufficient demand that you can normally sell it when u r done for what you paid for it (range of $125-$175).
By Section:
Verbal: McGrawHill and Dr. Collins
Reading Comprehension: ExamKrackers 101 Reading Passages (or some similar name)
Chemistry: Kaplan for Gen Chem. ExamKrackers 1001 Organic Chem Problems for Orgo
Biology: Kaplan is all you need for this. Taking a cell bio course can only help but Kaplan is enough on its own. If you want, supplement this with ExamKrackers Audio Osmosis CDs.
Math: Buy both Schaum's OUtline books mentioned. And Practice, Practice, Practice. All the other sections you can get by by knowing the concepts but math, you have to be able to put it into practice quickly. I did over half of the problems in each book to get comfortable and faster. Also, it sounds stupid but practice you multiplication tables. It will shave a couple seconds off each question and decrease the chances of making a simple math error.
Writing: Kaplan has some good pointers. I would suggest getting together a list of topics, writing 30 minute essays and then going to your school's writing center to have them evaluated and get pointers on how to structure your essays better.
Hope this helps.