Summary

I took whosawhatsis' thing 6499 eccentric sphere gears and modified it to have a base for a motor mount and battery pack.
I also converted the scad file and all the gears into STEP files so further editing can be done.

https://www.youtube.com/watch?v=eTZe9pc2b6g&feature=player_detailpage

Instructions

I printed everything at one time with support under the base only. I used 2 shells and 20% infill.
The motor is a 25mm gear motor with a 4mm shaft. you can buy them on amazon fairly cheap. I used a 20rpm set-up 3v motor. I bought some faster motors but they lacked the torque to drive the gears. This is a link to the type of motor I used http://www.amazon.com/Mini-25mm-Torque-Electric-Motor/dp/B00BX6FQEU/ref=sr_1_11?ie=UTF8&qid=1409407042&sr=8-11&keywords=gear+motor
The battery pack is a "AA" 2 cell pack with switch. I have a tone of these lying around and I use them on all sorts of things. You can find them at radio shack or online. the model is SBH321AS. You can also find them on Amazon here http://www.amazon.com/Battery-Holder-Storage-Leads-Switch/dp/B00IOFJYIW/ref=sr_1_11?ie=UTF8&qid=1409407312&sr=8-11&keywords=aa+battery+holder+switch
After printing everything tap all the holes... Tap the hole behind the battery compartment for the motor set screw, tap the shaft of the center hub, and tap the holes on the center hub. I used 6-32 set screws to lock the center hub onto the shaft of the motor. There is a small window which you can put the allen wrench in to get to the screw. I also used another set screw to lock the motor in place. That is the small hole behind the battery pack. All the gears are held in place with 6-32 socket head cap screws.

Motorized Gear Sphere