Cookmate made by Tapmates [$1.99 - iTunes Link] for iPhone and iPod touch lets you tell it what you already have in your pantry and then finds you a recipe to use it.
The graphics are so beautifully rendered and the interface so user-friendly it makes choosing what to cook for dinner much less stressful. In fact, it's so easy that I even allow my 4 year old to help out.
Cookmate includes a grocery list that you can use to add and later check off any ingredient or items you may be missing.
There is also a user-based rating system for each recipe. On the downside, that means that if no one likes the high-rated meal you prepared, it is probably not the recipe but your cooking. ;)
Video after the break. If you try it, let us know what you think!