Here is an instructable for a Parallax Boe-Bot that uses bumpers to navigate its way through a maze.
Step 1: Create Circuit
Use the image shown above to create the circuit.
Step 2: Create Bumper
Use cardboard, tape, and two screws or nails to create a bumper like the one shown above.
Step 3: Attach Bumper to Robot
Use velcro or tape to attach the bumper to the front of the Boe-Bot.
Step 4: Connect Wires to Bumpers
Connect the wires to the bumpers as shown in the images above.