The Ezy Roller is a great toy for active kids. It takes no batteries and moves remarkably easily. Kids just move the bar back and forth with their feet, and it goes. The Ezy roller features a nice hand break (great when you hit a bit of a hill) and adjustable bars. It will adjust to fit kids ages 3 to 14 (or adults if they don't mind scrunching up a bit).
Here is a video of the Ezy Roller we made at our last sales staff meeting.