The best (and only) book I read to help me for the PMP exam is the Head First PMP book. It takes a bit of getting used to the writing style and some people find it a bit condescending. But it is a really easy book to read and they cover most of the things in the exam. I would really recommend this book.

The Guide to PMBOK that you can buy from PMI (www.pmi.org) itself is a good book for the exam, if rather a bit too dry (for me anyway!).

In terms of mock exams, I did the free test from Head First (www.headfirstlabs.com ). And also the free test on the PMI site. To do this you have to be a member of PMI which I highly recommend. To get to the free PMI test, go to Resources tab on the PMI website, then click on "Go to eReads & Reference" in the bottom left section of the page. Then search for "Q & As for the PMBOK Guide, Third Edition".

The following is a list of free mock exams for the PMI certified PMP exam that I found on the web. Obviously the more exams you can do the better prepared you will be.

http://www.headfirstlabs.com/PMP/free_exam/

http://www.ajithn.com/login.php

http://www.oliverlehmann.com/pmp-self-test/75-free-questions.htmPMConnection.com

http://www.pmconnection.com/modules.php?name=Web_Links&l_op=viewlink&cid=9

http://www.tutorialspoint.com/pmp-exams/pmp_mock_exams.htm

http://www.flashcardexchange.com/flashcards/list/287102

http://www.pmtests.com/packs.php

http://www.transcender.com/demos/

http://www.voightps.de/Free_PMP_Exam.asp

http://www.testprepreview.com/modules/pmp.htm

http://certification.about.com/od/projectmanagement/a/pmp_test_whiz.htm

http://www.certgear.com/products/preview/pmp_certification/index.html

http://www.pmpbest.com/lifecycle/