I have been trying to get in shape, but I haven't yet gotten myself a Nike + iPod sports kit. When I do, though, I will be sure to download these two Widgets that Nike has just made available (they are currently in Beta, but what isn't?). One widget tracks your challenges (you can challenge another user, or group of users, of the NikePlus website to challenges) and the other tracks your goals (the person above has a goal of running 300 miles in 30 days).
At the moment they are only available to registered users of the NikePlus website.
Thanks, Hugh C.