What I love about them is that there are lots of categories to choose from, you can create a recipe box, lots of the recipes are rated by other users, and you can adjust the number of servings to fit your needs.
One of the things I want to add is that not all of the recipes are 100% natural or use healthy ingredients so don't be afraid to substitute ingredients to fit your needs. For instance, if the recipe calls for margarine, I use butter. If it calls for white flour, I use whole wheat. If it calls for breadcrumbs I make my own or use Panko (http://en.wikipedia.org/wiki/Panko).
There is even an app on the iPhone for this site which makes it easy to remember what ingredients you need to buy at the grocery when you forget your list!