My friend Chris recently wrote a fun little program that creates psychedelic patterns inspired by color organs from the 70's. It was initially just a Windows executable - but with a nudge from me and some help from our friend Dewb, I convinced him to package it up as a cross-platform FFGL plugin. It's available now as a free download on SourceForge and GitHub - a nice addition to any VJ's toolbox.
If you enjoy it, be sure to give Chris a shoutout - either here, or through GitHub/SF. Positive feedback is the best enticement for more goodies like this one.