Supercook is a pretty darn awesome site, where you enter the ingredients you have and it gives you a list of recipes you can make with them. It assumes you have water, salt, pepper, and sugar (sugar is a pretty big one), so I've been trying to find the largest number of recipes for the smallest number of ingredients. So far, it's butter & onions (12 recipes)...

Update: make that butter and flour (79 recipes).