College Board: The provider and AP program coordinator has made sure you know exactly what to expect on the exam and has provided you with a number of sample question to practice with. For previous exams, click here.
UC Davis ChemWiki: As a graduate of UC Davis, I fully endorse their ChemWiki site which is a quick reference - and easy textbook substitute - for anything chemistry. This is, furthermore, a college-level site, making an excellent resource to ensure your AP readiness.