Today Google has launched 3D versions of the main venues of the Beijing Olympics which you can view in Google Earth, or with their Earth API plugin. There are now over 35 new detailed 3D models of the stadiums and game fields already visible in the new satellite photos (taken less than a month ago). Check out Earthswoop to get a look at the 3D Beijing views (more of the stadiums will be added to EarthSwoop soon). Or visit Google Earth itself to get complete control and see descriptions of each venue. And Google has released a live Google Map mashup for tracking the games called 2008 Summer Games.
If you just want a taste of what it looks like, here is a video fly-through of the 3D Beijing Google has released:
[UPDATE 9-AUG: Google has offered a new layer which you find under the Geographic Web->Places->Summer Games 2008. It results in a bright red Olympics icon over Beijing which when you click on lets you load a new "Explore the Sumer Games" layer. This results in a network link which shows you Today's Events, Calendar, Events, and Venues. For each item, you are flown to the location of the event. Most of the venues are in 3D. There's a lot more 3D models than I realized in the collection!]