The definitive algorithms book is Cormen : http://projects.csail.mit.edu/clrs/ I think you should study this book and here is the MIT course to go along with it : http://ocw.mit.edu/OcwWeb/Electrical-Engineering-and-Compute...

Learning about NP complete problems is interesting to avoid certain pitfalls and mapping one problem to another is always a valuable technique, but it seems you are fairly new to analysis of algorithms so imho (having been a phd student focused on algorithms) this book and course is a great place to start.

http://www.amazon.com/Algorithms-Creative-Approach-Udi-Manbe...

this is also very good