Use one of these to keep track of what you eat (and in most of them – how much you exercise). Tracking your food is a good thing to do for at least a few days every several weeks or so. It helps you to see what you may have been oblivious to. My major complaint with most of these sites are the goals they set for macronutrient (fats, carbs, protein). Recent studies call some of these numbers into question.
SparkPeople.com (seems to require a lot of personal information)