Here is a cool website I found today. It keeps track of your calorie intake, and also calculates your calorie output (exercise). It's really user friendly and stuff too.
Start by entering your information, and then click the "start your journal now" button.
Then you register so that you can sign in to your journal every time.
From there it's self explanatory and fun!
(does this sound preachy? i don't really care if you keep track of your calories or not, so i won't be checking in on you to see how it's going. you don't have to do it.)