Good books on mathematics for somebody who's only taken high school math?
mhartl: Take a look at Journey through Genius by William Dunham.  I read it after high school and ended up spending much of the summer with a straightedge and compass making geometric constructions.  It's not all geometry, though; there's plenty of other good stuff, including some gems from Euler and Cantor's incredible diagonal proof of the cardinality of the rationals.