I've been using sparkpeople.com due to the fact it was the first site I found that has a database of foods and nutrition information that I could use for calorie tracking, but there are other similar tools out there. There are big problems with the functionality of the website. The list of foods won't populate when I am searching "recent" or "favorite" foods, and I have to enter and re-enter my search terms. Then the list will finally populate but it disappears just as I am trying to choose what I ate from the list. Then foods that had an indicator onscreen that they were "added" for the day are not on my food log at all when I refresh the page or access my log from the phone app. And don't get me started on the buggy problems with the phone app! Sparkpeople is run by people with moderate scientific knowledge on weight loss-- not experts by any analysis-- but they are enthusiastic about their topic despite poor article writing, editing or soliciting skills. And there is clearly no one on their staff with current web design skills sufficient to compete in today's web market.
But hey, it's free. and if you already know how to use science to improve your weight and health the tools can be useful if you are patient with the poor functionality.