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.

The program looks like a spreadsheet, except that the columns represent a piece of time as it goes from left to right and the rows are the lights you control.  I make a dummy track that doesn't control anything called 'tap'.  I then tap out the song for every beat.  This gives me another visual of the song.  I then create another track called "tap slow" which is the same thing except it is just the 1st beat of the measure.