The software package I use is called Light-O-Rama. It is both a hardware and software solution. They sell the controllers that have 16 plugs on them. You control each plug, like a dimmer switch on the wall, with your computer. With their software you can turn lights on, off, % intensity/dim, shimmer and flicker. The challenging part is to get the lights to do something fun with the flow of the music.
... to be continued