Today Google has released Sketchup, a 3D drawing desktop application. From the little demo animation that they have on the linked page, this looks like the rare combination of a very powerful, yet easy to use tool for creating 3D renderings. Renderings can also be used in conjunction with Google Earth, presumably as some sort of a layer or overlay.
Unfortunately, the Mac version of it is ‘coming soon’ even though the pre-Google acquisition product already ran on OS X. I’ll have to wait for the Mac release to get into this any further. I hope that the delay is something a simple as switching over the branding and a few other minor tasks it truly will be available RSN.