^Schaum's for College Physics, College Chemistry, Calculus, etc.
I actually have all of those LOL but I didn't use them extensively.. I thought some of the problems were too hard/structured differently from the types of questions I encountered in class. If you have AP prep books for classes like physics, chem, and bio, they can be really helpful in explaining some of the concepts and fill in gaps that your lectures might not be covering. However, you should realize that the hard questions that you have to answer correctly to get A's won't be found in those books and are instead answered based on a mastery of all the big and small concepts and building a strong intuition for those concepts.
A lot of people find these videos helpful:
http://www.freelance-teacher.com/videos.htm
I used a lot of the ochem ones and if I remember correctly they were pretty helpful.
For practice problems.. it really depends on your course. You should prioritize finding old tests for your professor through friends, test banks, etc. If you can't find any, just do all the problems your professor assigns and if you finish those, do any problems you can find in the textbook. You won't necessarily benefit from random practice problems online if they're nothing like what your course/professor tests on.
