Paul Vidich, Taylor Mendelsohn and Max Guyton's project for CS 228 (Spring 2008): The robot is controlled via the arrow keys on a laptop over a bluetooth connection. An ultrasonic sensor recognizes an object in front of it and activates the intake tread. Once the object is far enough inside, the ultrasonic sensor queues the motor to stop.
A light sensor is also constantly detecting the reflectivity of the surface under it. When the light sensor detects it's over the paper as opposed to the table, it operates the tread in reverse, releasing the payload.