A giant, easy to use site with recipes for every meal, arranged by category or alphabetical. 
 

Cook's Thesaurus :  http://www.foodsubs.com

Suggests substitutions for over 1,500 cooking ingredients, including low-calorie and low-fat alternatives for dieters, inexpensive substitutes for gourmets on a budget, and innovative replacements for hard-to-find ethnic ingredients.  Searchable. 
 

Nutrient Data Laboratory Food Composition Data :  http://www.nal.usda.gov/fnic/foodcomp/search

Search the USDA Agricultural Research Service's database for the complete nutritional content of individual food items. 
 

RecipeSource :  http://www.recipesource.com

Formerly SOAR, the Searchable Online Archive of Recipes, RecipeSource searches the archives of more than 66,000 recipes.  Includes ethnic foods as well as special diets.