I've always loved the way the top of the Empire State Building is lit in appropriate colors to celebrate various Holidays, blue for Hanukkah, red and green for Christmas and so on. Its not just the big Holidays that they mark either and when we lived in NJ I always enjoyed the "guess what the Empire State Buiding is lit for tonight" game, often it would be a sports related theme that meant I had no chance of guessing correctly.
Recently they have taken it to a whole new level with incredible light shows, there was a wonderful one for this year's Fourth of July celebrations and they really pulled out all the stops for Halloween. Apparently Marc Brickman is the artist behind these light displays, go Marc with your dancing lights*!
*I'm pretty sure "dancing lights" is the correct techincal term.