Tiny programmable module featuring Microchip’s PIC18F25K50 microcontroller. It packs a Micro-USB interface and 16 digital input/output pins onto a 1″×0.6″ board and ships preloaded with a USB bootloader, so no external programmer is required. Pololu 3150

The A-Star 32U4 Mini LV is a programmable module based on the ATmega32U4 from Atmel. Unlike competing products, it has an onboard switching step-up/step-down regulator that allows it to be powered efficiently from a 2.7 V to 11.8 V supply. Pololu 3103

The A-Star 32U4 Mini ULV is a programmable module based on the ATmega32U4 from Atmel. Unlike competing products, it has an onboard switching step-up regulator that allows it to be powered efficiently from a 0.5 V to 5.5 V supply. Pololu 3102

Kit includes all the basic mechanical parts to get up and running, including two motors, two wheels, one ball caster, and battery contacts. Pololu 3500

Pololu low-power miniature engine, with a 15:1 transmission, shaft speed is 1400 rpm, torque is 0.2 kg * cm (0.02 Nm). Pololu 4783

Metal Worm Gear Motor, 3 RPM Rotation Speed, 12V Working Voltage. JGY370-28

Metal Worm Gear Motor, 30 RPM Rotation Speed, 12V Working Voltage. JGY370-29

Metal Worm Gear Motor, 50 RPM Rotation Speed, 12V Working Voltage. JGY370-30

Metal Worm Gear Motor, 66 RPM Rotation Speed, 12V Working Voltage. JGY370-31

Metal Worm Gear Motor, 100 RPM Rotation Speed, 12V Working Voltage. JGY370-32

Metal Worm Gear Motor, 160 RPM Rotation Speed, 12V Working Voltage. JGY370-33

Metal Worm Gear Motor, 237 RPM Rotation Speed, 12V Working Voltage. JGY370-34