Cambridge 3U is proberbly the best for practice questions. The development questions are the best for practice, and they're not hard enough to need worked solutions, even though they're more than hard enough for 3U exams. Extention questions are a waste of time mostly. It's totally irrelevant, and most of the time, I have no idea what they're trying to ask, although some of them are quite good.
Texts books arn't that good, especially for people who have trouble trying to sit down and study, (like me). What i found is that doing practice tests and past papers is the BEST method to study for tests. Just do a few past papers, and once you get over 90% in those, you're proberbly going to get >90% in your actual test too.
Math in Focus is a joke. Their questions are not worth doing, it's a major waste of time. Just stick with the Cambridge book or past papers.