Through socialspark I have discovered a new online game for kids called ActionAllStars.com. I logged in and tested it to see if it would be good for Ben. It's great! First thing you do is set up your avatar and then launch the game. I did have a slight problem with not receiving their activation email in my comcast.net account, but I signed up with my gmail one and that came through fine.
I played a snowboarding game which was really pretty fun - I accidentally had to play it three times because it was so fun. ahem. Here's a screenshot of me doing a half pipe or some sort of snow board nonsense.
If you are looking for a more sporty alternative to webkins or build-a-bearville (which frankly are a bit too frou frou for my tastes) this site might be for you. They have licensing agreements with the sports leagues such as mlb.com and nba.com so boys will think its cool. Its also a safe environment for kids. I especially like the way you can let the kids chat, but it does 2 different kinds of "safe chat." I like the one where they can just pick certain canned things to say. This is a good way to introduce a bit of online community without worrying about what your kid is saying in any chat.
Basically, this is a free, fun, and safe way for kids to play online.