In the past few months, we have covered plenty of awesome educational robots here. Geekbot V2 is a handy kit that comes with everything you need to build a rover robot. The GeekBot Rover has a payload capacity of 2.2 lbs. It comes with a rechargeable 4400 mAh battery. The robot is powered by an Arduino compatible microcontroller.
You can always add sensors to do more with this kit. The kit comes with servos, wheels, mounts, chassis, buzzer, and almost everything to get started. You can get yours for under $150.