Google Releases Sketchup for All. Google has released a free version of SketchUp (video and tutorials), quite possibly the coolest and most intuitive 3D authoring tool. An added bonus of SketchUp is it's integration into Google Earth. Google has also provided a 3D Warehouse for the posting of your models, which can be downloaded into either application (SketchUp for editing, Earth for displaying). Kind of gives you some insight into their plans for using Google Earth as an Automotive (Honda and Volkswagen) GPS service. (Sidenote: how long until this is seen as a threat to national security?)
J-Track 3D is an interesting JAVA web-app offered by NASA which gives a 3D interactive display of over 500 satellites currently orbiting the Earth.
Use the free 7 day trial while it's available! This lil program lets you zoom in pretty darn close on just about any spot in the world. And it is FREAKING COOL. I don't have much better commentary than that, sorry. You can zoom around to your favorite locations, tilt the camera, show all road names, rotate views - and once you've got a bunch of stuff plugged in its really neat to just click between them and watch the flyby. I can't believe this isn't a double post, but couldn't find it on search. Have fun!