Meal Snap is a pretty neat app that photographs your food, uploads the picture, and then replies with a calorie count in just a few seconds.
This seems like the sort of thing that wouldn't actually work, but it's surprisingly impressive. I took pictures of some leftover steamed veggies in my fridge and it gave me a pretty accurate calorie count. While I can't be sure, I'd imagine these counts are looked up by actual people as you get a faster response if you name your food rather than simply photograph it. That said, I took a picture of some brownies I made last night and, although Meal Snap's horde of calorie counters thought it was chocolate cake, the calorie count was pretty much spot on. It even gave me a calorie count for a bag of dog bones. It's fast, it works, and is excellent if you're trying to count calories but hate the tedious task of looking up every food you ate after every meal.
Meal Snap is available on the iTunes App Store, right now, for $3.99.