My friend Frugalina is using a FREE online site for keeping track of what she eats and her exercise: "MyFitnessPal.com" and another friend was talking about "SparkPeople.com". So of course, being the masochist i am, i logged into both to compare my day's food and exercise. (i have thoughtfully logged out of both sites before adding the link, just in case it might take you to the unhappy place where i had to log in last night's ice cream. Chocolate peanut butter cup, mmmm....as in "mmmmany calories!!!!!!!")
Both have their strengths--My Fitness Pal is a bit more straight forward, easier to read for me. Less fussiness on the page. But Spark People has a better/easier food database. Both have ways to track most types of exercise and regular activity, and show you how that impacts your day's calories, since the additional activity earns you more calories.
In my perfect world, using my laptop computer for hours a day doing email, genealogy and blogging would earn me extra ice cream points, but alas, they expect you to get off your butt and move a little.
In the past i had used a free trial of a software called "Calorie King" that does pretty much the same thing, but for a price. Now, their food database was a thing of beauty--even more extensive. But it did cost something.
More differences between My Fitness Pal and Spark People: Spark People gives you the opportunity to track more than the basic nutritional bits like fat/carbs/protein. You can add a ton of different vitamins and such to track in your food choices (she said, carefully avoiding the word "diet.") Both give you many opportunities for Community support at their websites, but only My Fitness Pal gives you the banner at the top of the page with other weight loss sites amusingly titled things like "weightloss4idiots."
All in all, as Frugalina said, and like i've learned before in my 50+ years of battling the bulge (and losing TO the bulge,) "it makes me more aware." And that has to be a good thing.