Stack Overflow
I just found Stack Overflow and its getting nearly an addiction for me. It’s an awesome site where you can post questions/answers in all kinds of programming topics, with a point/rank system that rates both the quality of the questions as well as the quality of the answers.
I found there answers to questions that were bugging me for quite a while, and browsing the top questions is a great resource for knowledge.
Visit the site or the wikipedia entry