The all-seeing dots (Google Earth)

Ok--wow.

Don't blame me for how much time you'll spend staring at it, but this is one of the coolest things I've seen in a while. It makes all other map tools look like cuneiform clay tablets.

Check it out: http://earth.google.com/

I would heavily recommend a broadband connection for the experience, but it is well worth it. There's a lot of features here, so keep trying new stuff!