The one I use by far the most is RecipeSource, followed by AllRecipes. Others include:
There are a few others I'll visit occasionally, like Epicurious.
I'll tell you, if you haven't discovered La Belle Cuisine yet, you're in for a big treat. It bills itself: "La Belle Cuisine: Fine Cuisine with Art Infusion. Our goal is to provide a beautiful, relaxing atmosphere, designed to inspire, entertain and inform you." It lives up to its billing. It's a potpourri of recipes (fabulous recipes), food quotes and great artwork. Be prepared to stay a couple of hours.
It's at http://labellecuisine.com/la_belle_cuisine.htm