So I was messing around, checking out google stuff to go with my shiny new wave account, and stumbled across this on their blog:
http://googleblog.blogspot.com/2009/10/introducing-google-building-maker.html
Google Building maker.
We like to think of Building Maker as a cross between Google Maps and a gigantic bin of building blocks. Basically, you pick a building and construct a model of it using aerial photos and simple 3D shapes – both of which we provide. When you're done, we take a look at your model. If it looks right, and if a better model doesn't already exist, we add it to the 3D Buildings layer in Google Earth. You can make a whole building in a few minutes.
Basically, you load up the app in your browser, and it looks just like google map with a bunch of pins in it. Pick a pin for a city you want to build in, and it'll zoom you in. It shades different regions for where buildings are already made, and where they need to be built.
Center your crosshairs on a building you want to make, and click go...
It'll load you into an isometric shot of the building, and you start building your wireframe on top of the picture.
As mentioned, buildings are created on top of 2D aerial images. These images or photos were taken by aircraft at some angle to the ground, allowing you to see not only the top of buildings but the sides as well. These images, called oblique images, resemble how people normally view their world compared to traditional top-down (orthogonal) photos.
Once you get it where you think it's good, click next. It'll spin the view around to a different angle. And you thought your model was good. Ha! Think again. Now you re-align the boxes with the building and rotate, repeat.
When you've got it all nice and lined up in all the side views, you
can save it, and it'll upload, google will review it, and
eventually push it out to google earth. Neat!
But screw that. That's too much work. Wanna know what I found out? Click that little "viewer" link up on the top left. Bam! See your newly textured 3d building in amongst all of its 3d buddies! Also see the sad, lonely 2d buildings that haven't yet been built. Man, looks like you've got your work cut out for you. Go to it!
See, in this example they were lazy. As you could totally build out the air-conditioner on top, etc.
(You will need the google earth browser plugin, which it offers to install if you don't currently have it. You'll also need a google account if you want to save. So, fair warning to the tinfoil hat crowd.)