simplyrecipes is probably my favorite, I cook a lot of her recipes and many are in permenant rotation at our house.
I read the Pioneerwoman but I am sort of lukewarm on some of recipes. I enjoy the overall site.
I used to find some good ones on CityMomma but it is more of a regular blog site then a cooking site.
I really enjoy CheapHealthyGood. I don't cook much from it but I really like the content.
The steamykitchen is fun.