i keep saying 'whoa.'
Google Maps -- making driving directions actually fun.
(Just wait until they enable an overlay of satellite imagery from Keyhole with one click. Then someone will write a bookmarklet-y thing to transition from a zoomed-in Google map to an Amazon street-level photoset. And then we'll never have to leave the house -- we'll just buy huge monitors and pretend we can fly around the country like Chris Reeves did in Superman.)