Check out the Robocut, a lawnmower robot with Basic Stamp as controller. You can even buy the kit so you can build one yourself.
Now, if you can get one of these DIY kits and make it solar, that’d be something to watch.
“RoboCut, is a BASIC Stamp powered robot. Two 12Volt motors with gearbox gives the two large drivewheels good traction and the robot can manouver in very small areas. Powersource is a NiMh accu-pack at 12V, 4.1 Ah. One motor gives the cutterdisk a rpm at approx. 3500 rpm. A Basic STAMP 2 is the brain in the PCB