In my quest to get a better feel for how many calories there are in food, I've started using
mynetdiary.com. As mentioned before, I don't do "diets", and I don't want to become a calorie-counting obsessive, but as a rough guide, it seems like a good way to get a grasp on how it all works. Because I really don't have a freakin' clue.
You can log exercise as well as food (ie how many calories you're burning as well as how many you're consuming), and it gives you a daily balance sheet of calories in vs calories out, as well as breaking your food intake down into carbs/protein/fat/fibre etc.
There's a good range of preset food and exercise types in the database, but it's also customisable so you can add your own food and exercise types if you can be bothered to go into that much detail.
And it's available as an iPhone app, which is why I chose this one rather than some of the other similar sites on t'web.
d.