i use fatsecret.com to track my calories consumed and burned (it's free, and the pick list of foods and restaurants is extensive which makes it fast for me):
fatsecret.comand if you want to see what the impact will be over time, this body weight calculator can help turn calories (like those from fatsecret) into pounds over time:
fatcalc.com/bwpit is good enough it can make a projection based on how active you are vs what you are eating on a regular basis.
*edit: fatcalc.com no longer allows for calculations that go well beyond the "acceptable" bmi range.
i just tried to update mine, and it wouldn't give me the calc to 400 lbs.
i guess too many of us fatties were using it for "unhealthy" purposes