It's not surprising that having a mobile operating system from the guys at Google means you're going to get some pretty fancy implementations of Google Apps. One of the great features that the HTC Dream offers thanks to its Android OS is the compass mode when viewing Streetview in Google Maps. It uses a combination of the phone's accelerometer and GPS to create a compass, that when combined with Streetview, will show the street in 360 degrees as you rotate your phone.The best part is, you can do it anywhere in the world, right from your phone. It also works when you point the phone both up and down, tilting from the sky to the ground.
I'm certain there are a whole range of practical applications for this that I can't think of (considering it is Friday afternoon), but even if there aren't, this is one of the coolest features I've seen on a phone in a long time, and it's built right into the OS.
[HTC Dream on Giz] By the way - apologies for the video quality. I had to shoot indoors to be able to see the screen, which affected both the shooting quality and the compass' accuracy.