Are there any free practice AP tests online? Best books for Calc, CS, Lit?

Starting late, but my son will likely take AP Calc A/B, Computer Science and possibly English Literature. We don’t have any study guides and I’m unfamiliar with what are the best tools for any of these subjects.

My son is homeschooled and taking (or has taken) these subjects at the local community college, but will go ahead and take the AP exams, too, just to cover his tracks for what might transfer since we don’t yet know what college he’ll be attending. (He’s a senior)

Thanks for any guidance.