I used Aho, Hopcroft, and Ullman's two Algorithms books in class. They are old but extremely good. If you want to buy dead tree books they're available used for a very low price.
Hope that helps.
(I didn't really mean to recommend Sedgwick's stuff. As I said, I just think it's not bad.)
Some people might find it as a downside but the book was written with Java in mind. I personally didn't mind this at all.
http://www.amazon.com/Algorithms-4th-Edition-Robert-Sedgewic...
[1] http://www.amazon.com/Introduction-Algorithms-Thomas-H-Corme...