The Velleman VM116 USB Controlled DMX Interface Module can control DMX fixtures using a PC and USB interface.
Test software and "DMX Light Player" software is included, a DLL is provided to write your own software.
Furthermore there is a stand-alone test function that outputs all 512 channels at a time, with adjustable levels.
Also available in SELF-ASSEMBLY Electronic Kit format:Order Code K8062Features
Here a link to a enlightening and amusing presentation of the K8062/VM116 along with a nice light show and plug for Quasar!