Have you checked out the colleges in your area? Taking the course in person will be so much more helpful than online. I studied through American Council on Exercise at a college and am very happy.
If you must learn on your own, ACE is extremely helpful with many sources.
Good luck and enjoy.
NASM (www.nasm.org) also has an option for online / self-study. When you think that you are ready to take the test, you go to a location near you. This is a company specializing in the administration of tests. When I did it, it was about 10 miles away from me. Optionally, you can go for a weekend workshop.
Wish you success.