i liked the fountainhead, it was hard to stick to tho.
hrm, I'd definitely suggest the oldies,
the decameron by boccaccio (its interesting, i think it was the 14-somethings and its set during the black plague. some weird stories in there)
the dialogues of plato by (duh) plato (I saw the apology of socrates recited by the amazing yannis simonides, if you ever have the chance i would definitely suggest it)
shakespeare, no matter how over-rated he is his work comes up a LOT in any sort of english what-have-you.
the ramayana, either in the epic poetry verion or in a more prose version. its interesting.
dare I say it, the bible. it is really interesting as literature, me and my english teacher had many an (after-school) discussion about it.
more modern type things:
1984, as sold has already suggested (loooove it)
to kill a mocking bird, as also already suggested by burning_sands...
Life of Pi by Yann Martel (its interesting, somewhat religious undertones- the main character is christian, hindu, and muslim all at once- but an interesting story nonetheless. i want to be on a life boat in the middle of the pacific with a tiger, a zebra, and orangutan, and a hyena)
As I lay dying by William Faulkner (weird, hard-to-read book but just. weird. only word for it, really)
all of roald dahl's short stories (looking for more dark tings? go to these, fo shizzle)
the perks of being a wallflower (short but interesting anyway)
gandhi on non-violence, edited by thomas merton and preface by mark kurlansky (i've just started reading it, its interesting)
if you had any interest in greek or roman times try the greek way by edith hamilton. incredibly flowery writing and you have to read it over a good three times to understand exactly what she's saying, but its beautiful. shes also the sister of the actress who played the wicked witch of the west.
if you had an interest in art history I'd suggest the rape of the masters: how political correctness sabotages art. i love how he bashes the art historians, its awesome.
i have a lot more but i think i should cut it short lmao.