Two new zoom levels are now available in 'Map' view that extend the existing 'pseudo 3D' effect to full fledged to scale building outlines. So far 3D building support seems limited to US cities. I've been able to view the enhanced building outlines in New York, Los Angeles, Boston, and Chicago.
With any luck they'll extend this to every building available in Google Earth -- and then every building available via public Sketchup models. Then all we need is textures on the models.The biggest zoom level is quite impressive -- here's the Chrysler building in New York
Google Maps isn't the first to offer the 3D view, Live Local has been offering it for a while, but it's a welcome addition to the increasingly impressive Google Maps service.