I built a robot in four phases: frame and motors in college, shaft encoders with 6800 microprocessor displaying position on 4014 display at Tektronix, h-bridge motor drive from Teensy2, and, Mac/Txtzyme wifi photobot with friends at Dorkbot.
Frame
Scrap aluminum came from a flip-chart easel.
20:1 gear reductions came from servo-controlled rheostats surplussed from theatrical lighting.
24v dc motors were found in the radio club junk box.
Drive wheels were once kid's training wheels left with me as part of a trick-or-treat gag.
With hacksaw and sheet metal screws I built a frame large enough to hold two lead acid motorcycle batteries on one side of the drive wheels and a computer and radio stack on the other.
Encoder
Wayne Downer hand-built a pair of shaft encoders that read the non-drive side of the motor armature.
I programmed my Wintek Control Module to decode the encoder gray code, compute the platform's displacements and plot its path on a Tek storage display.
I wrote this in Tesla as a stand-alone application.
We showed this at the company's Technology Fair. Most people though the attached terminal must be a 4051 workstation, not a 4010 dumb terminal.
H-Bridge
Wayne Downer built a motor controller for the robot but it never drove under its own power.
Jim Larson built a second motor controller and programmed one of my Teensy2 computers to make the robot dance.
YOUTUBE nE2kY3VFw4g Dancing under Teensy2 stand-alone control.
WiFi
I rewrote the motor control software as a perl script emitting Txtzyme commands. This ran on an old Mac laptop where it was exposed as a small collection of cgi scripts. github 
Step and Turn scripts would advance the robot by a foot or turn it by 45 degrees.
Dance would perform a small dance meant for enclosed spaces.
Blink would flash a 12-volt semi-trailer signal light I picked up at an auto parts store.
Wag would wiggle the servo-motor controlled foam core tail that I borrowed from earlier projects.
Brag and Sing would use Mac voice synthesis for short performances.
Click would take a picture with the digital SLR mounted on the robot with a Manfroto arm.
Scripts could be interleaved. I invited Dorkbot attendees to try operating the robot. My choice of cgi scripts made it clear that there was nothing fancy going on in the user interface.