Help me find good classical music, please.

[CardSharpCook]

OOT, I know very little about classical music other than I like it. Especially when I'm working. It helps me stay calm and stress free. I've purchased versions of the William Tell Overture and 1812. I was able to find them because I've heard of these works. I don't know any others. So help me compile a list of music to buy from itunes to juice up my ipod with some edumacated stuff.