This is a pretty cool little Google widget that you can put on your Google Homepage.
You put in your scale weight every day, and it tracks the moving average for you. I've found it useful, since I use Google as my homepage, everyday I see the widget, reminding me I need to enter my weight. Of course, right now, it's also screaming at me: "Danger! You're heading away from your goal!" So, that reminds me every day that I need to work out. This provides me with a nice little feedback cycle, which is what I need right now.