Paul Stoffregen manufactures a line of tiny microcontroller boards and supports them well with well conceived but still hobbyist oriented software. I buy blemished boards and hook them up to everything.
Teensy is in the same family as the Atmel AVR Tiny12 and smilar to parts used in Arduino. Teensy's advanced USB capability make it my controller of choice.
Codosome Hexis was an art project using a version of video circles extracted from my generated codosome files.
Uno the Integer was a simple test that evolved into an art piece exploring how we perceive whole in organized parts.
Txtzyme extends the reach of the USB bus to arbitrary electrical signals. It interprets throw-away programs encoded as single-character commands bundled into short strings transmitted to a USB enabled microcontroller.
Christmas Lights that perform new shows every day or two built with perl scripts and Txtzyme.