The glow ball installation was my gift to my friend Nadia on the occasion of her wedding.  
The installation consisted of 50 battery powered colour changing lights.  Each light consisted of three LEDs (red, green, and blue), a micocontroller, and support electronics built into a ping-pong ball.  The microcontroller randomly increased or decreased the duty cycle of each LED independently, causing the colour of the lights to slowly change over time.
The event was on the evening of July 7, 2007 in the back yard of a house in Cambridge.
Above, several of the glow balls gathered together at the beginning of the party.
As the night progressed, the glow balls were moved around by party guests and re-appropriated.  Above, some have been used to outline a stage.
At the end of the night Nadia gathered all of the glow balls together into a white paper bag.  The bag glowed with many different colours, all changing.  It looked as if it contained the smoldering embers of a fantastic rainbow coloured fire.
This is the PCB I designed for the project.  The large footprint in the picture on the left is for the battery holder, which was a standard CR2032 battery holder modified to hold two batteries, which were needed to provide the voltage for the blue LED.
I did everything for this project, including idea conception, circuit design, PCB layout, microcontroller programing, and assembly.  My good friend Dan Good helped a great deal with assembly.  
PCB layout was done in Protel.  The microcontroller was an Atmel ATtiny13 and the code was written in C.  The micros were programed using avrdude on a MacBook Pro running MacOS 10.4 with an AVR ISP mkII USB programmer.