Check out this video of 20,000 Christmas lights synchronised with music. (Be patient, it takes a few moments to load.)
This was in Newmarket, Ontario, in 2006 to raise money for the local Hospital. I'll have to investigate if the same display has been plugged in this year.
The part I like best is the electricity meter spinning round! Rather him than me.
Amazing display, but I'm glad that I'm not one of his neighbours!