Great thread! I'm sure someone will need this information, so I'm bumping by adding my own experiences.
I've tried fitday.com, sparkpeople.com and nutridiary.com based on the recommendations of others. I think, like a previous poster mentioned, you have to play around with them to see which one suits you. Initially, I was very frustrated and thought I'd never get the hang of it. But now I keep track of my calories everyday. It's helpful for knowing how much I can eat before gaining weight. I like to see my average calories, protein, carbs, etc., too. I am a carboholic and this way I am accountable. It's scary when you think you haven't eaten
that much, then plug in the calories and

Foodwise, it all goes to hell for me at this time of year anyway, but come January 1 I start eating clean again, watching the portions. It only takes me a few weeks to get back to my "happy weight." I don't believe in suffering!
Good luck to everyone!