There are the motorized lego technics sets. They run about $100-$200 each. Not all the technic sets are motorized though, you really have to read the description. Some can be motorized but you have to buy the motor set separately. It's a bit confusing, IMO, but it's a nice step up from Legos without investing in Mindstorms. http://technic.lego.com/en-US/Default.aspx

(My DS7 has been telling everyone he asked Santa for Mindstorms so that's what he's getting for christmas! I hope he's not too sad christmas morning!! I wish he was willing to get over Santa alraedy!)

~amy