How to Cook Everything is my new favorite app and I haven't even made anything with it yet! Mark Bittman from the New York Times had one of the top rated cookbooks (printed) this year and then he went and had an app made for $5 with all of the recipes, hints, lists, and illustrations! It's amazing. I'm all for printed cookbooks, but this one is definitely more transportable and about $25 cheaper!
It's got essential recipes for all the basics and covers food from a variety of cultures including France, India, and Africa.