BEAM is an acronym standing for Biology, Electronics, Aesthetics, Mechanics. While BEAM robots are often simple (consisting of a solar cell , motor, 2 transistors , and capacitor ), robots as complicated as 8-jointed, 4-legged walking spiders have been built using the principles of BEAM.
Solarbotics.net - BEAM Reference Library
The BEAMAnt is a phototactic bot which has potentially complex behavior depending on the light level. It has two photodiodes for light sensing, and two antennae which switch the motors into reverse when they touch something.
Mechanisms and principles
The basic BEAM principles focus on a stimulus-response based ability within a machine. The underlying mechanism was invented by Mark W. Tilden where the circuit (or a Nv net of Nv neurons) is used to simulate biological neuron behaviours. Some similar research was previously done by Ed Rietman in 'Experiments In Artificial Neural Networks'. Tilden's circuit is often compared to a shift register, but with several important features making it a useful circuit in a mobile robot.
BEAM Robotics - Wikipedia
Solarbotics offers robot kits, solar-powered robots, books, electronic components, motors, parts and information on the expanding field of BEAM Robotics.
TomboT - and the home of Liverpool Universities BEAM robotics
"Myself and some friends demonstrated to the University how simple robots can be built which provide an excellent learning platform, and as a result the University have changed the way they utilise their Year 1 lab sessions to include our robots". - Tom Elner
One more nice site BEAM Robots and also BEAM Online.