NoobToob and Escapist, mostly. If I don't feel I have the answers I want yet, I'll try GamesRadar and GameFaqs. Consider the latter two less useful since I rarely agree with GamesRadar writers (still give some good information on games, though) and GameFaqs is completely inconsistent in quality.
Although GameFaqs isn't entirely useless if there are several reviews. I generally read the highest and lowest score and a few of the averages. This usually gives me a pretty good idea of the pros and cons of the game and the mechanics.