I took a philosophy course last semester and I really enjoyed most of the dialogues of Plato (the earlier dialogues are Socrates' thoughts which tend to bleed into Plato's philosophy in the later dialogues)
http://www.amazon.com/Great-Dialogues-P ... 0451530853 (its like $6.60)
Plato is a really good start for anyone who is starting in philosophy and his ideas are reasonable.
We also read Aristotle (I didn't really like him as much as Plato), Descartes (interesting but I had a few problems with philosophy), Hume (crazy nihilist), Siddhartha (crazy) among many others. These are some key philosophers that if you are looking to read into philosophy would be a great start.
My personal favorites are Karl Barth (German) and Søren Kierkegaard (Danish), however they pose a more religiously oriented argument