Green Kitchen was just featured on Apple's best of 2012 list -- it's a really well-designed cooking app with a focus on healthy recipes. It's all based on the Green Kitchen Stories blog, so looking through the content over there will show you what the app is all about: Healthy, interesting food. It's not necessarily the more traditional staples, so if you just want a heads up on how to cook some simple items, you should probably look elsewhere (I personally really like the How to Cook Everything app if you want a more straightforward cooking experience).
But the Green Kitchen app does have some good and interesting ideas, and everything is organized well. Once you choose a recipe (which you can find either in a list or by browsing through big pictures in the app itself), you get an interactive list of instructions that clearly guides you through each step of the recipe. And throughout the whole process, everything is very clean and smartly put together.
The app's big drawback is that while it is fun to browse through big pictures of the recipes, if you're looking for something specific (like a certain dietary restriction or a central ingredient), you just have to drill down through the recipes in there. There aren't a lot of recipes, either, especially compared to bigger and older apps. But more are being added all the time, and again, this isn't a traditional cookbook: It's more a nice list of options when you want to try cooking something different. Green Kitchen is available in the App Store now for US$3.99.