Taking AP's on your own is totally doable. My school didn't offer any and I took six. In my experience, as nydwracu said, AP Psych is easy. So is Environmental Science and English Lit (if you do well on the english sections of the SAT). World History is interesting, and easy if you like memorization. I've heard Human Geography is easy too. The AP exams of languages that are commonly spoken as first languages in the US (Spanish, Chinese) tend to be harder than the ones that aren't (Latin, German) because native speakers drive the average up (it's not exactly graded on a curve, but they don't want too many people to get 5's, far as I can tell). The language ones can very often get you out of the language requirement in college, which frees up a lot of time.