I use MyFitnessPal, which I find to be a great iPhone app and an acceptable web interface. Other people have said they're really happy with LoseIt, which is similar.
MyFitnessPal is great for entering what I'm going to eat, looking up the calorie counts of things--it has a really extensive database. For exercise, it also has a database of how many calories are burned during the exercise. (Some say it overestimates these)
Hope this helps!
Goal: Back to where I was!