This long-motored 360:1 Mini Metal Gear Motor is a torquey, compact brute!
Looking for a good continuous-rotation servo? The Grand-Wing Servo GSV0008A is a well proven unit!
This tiny unit from GWS comes with a ball-bearing supported shaft, Futaba connector, and accessory kit.
Didel specially made nice aluminum brackets to fit the GM17 gear motor. Super light for very efficiently built robots!
Here's a really cool quadrature encoder and motor driver for the GM17 Gear motor designed by the micro-specialists at Didel.