The most amazing piece of free software you will ever get. After buying Keyhole, Google has released the product after a long hibernation.

Just like God you can tilt, rotate and zoom into almost any point on US - except maybe destroy and create

Things to do:

Add Layers : Particluarly 3D buildings. 3D builtings have been implemented only for metro cities (like NYC, Seattle). They are just awesome.
Play Tour Put some driving directions and hit PLAY. You now have a helicopter tour from Point A to Point B
Tilt and Rotate - Its no fun to just look from the top, hit tilt and now you can see everything in any prespective.
Drag and Leave - After tilting, drag the map and leave it, you will have a wonderful tour of your neighbourhood.
Update: They have pulled the software back. I have a copy if anyone needs it.

For those of you outside US, here are some US addresses you can play with.
700 5th Ave , Seattle ,WA
144 W 19th St New York, NY 10011

Some US zip codes - 98040 (Mercer Island) 02886 (Warwick, RI)

And if you really want to knock yourself off the chair - checkout the mountains at a prespective. Pick a mountain range in Montana or Rockies - tilt the angle a bit, do a wee bit rotation - and the graphics could easily pass off as the title sequence of CliffHanger - so realistic 3D mountains.

1) go to : West Glacier, mt
2) Zoom out a bit
3) Go north and tilt

Google Earth never stops to amaze me.