BlinkStick is a DIY open source USB RGB LED. It's small, the size of a USB flash stick and designed to be easy to assemble.
You can find more details about it here:
This repository contains the firmware required for the ATTiny85 chip.
Details about setting up the development environment will be released soon.
Released under CC-BY-NC-SA 3.0 license:
http://creativecommons.org/licenses/by-nc-sa/3.0/
(c) 2013 by Agile Innovative Ltd