Here is the simplest possible no chassis bot. As i did not have any cardboard at home i tried out something that worked out miracles. Try this out i made mine in about 10 minutes you need not solder (well i did not).
Step 1: Get the Stuff
2x motor (Bo series 2) 150-300 rpm
Now you could shoot off to making it.
Step 2: Prep the So Called Chassis
use double sided tape to keep the motors intact.
Step 3: Some More Taping
use brown tape and then truss the motors securely
Step 4: Finish
attach the wheels place the 9v connect one - wire to one+ and do same on other place then connect it to the crocodile clips.Finished.
Step 5: Vrooom
connect them to a battery vrooooooooooooom vroooooooooooooooooooooom