My favorite free attraction in Las Vegas is the dancing fountains (click for wmv video link) outside the Bellagio hotel/casino. If you've never seen it, you must. It's basically a huge water fountain that seems to "dance" to music. It's right there on Las Vegas Blvd., and it happens every fifteen minutes or so at night. You could literally sit there for hours watching the different arrangements to the different songs. very cool.
The point of my seemingly random endorsement of a Las Vegas attraction is to direct you to this video link of a house decorated with Christmas lights. Christmas lights that appear to "dance" to rock music in the same manner as the Bellagio fountains. Pretty cool. Pretty, pretty, pretty, pretty, pretty, pretty, pretty, pretty, good.
Link from: http://john.hoke.org/