Virtual Earth 3D is now available at Live Search.  Click on "3D" on the navigation control to enter 3D mode.  Here's a direct permalink to Virtual Earth 3D:

http://maps.live.com/default.aspx?v=2&cp=46.935893~-99.71&style=a&lvl=3&tilt=-90&dir=0&alt=12800519.899355

With this release, the Virtual Earth API's have also been updated to version 4 so you can create 3D mashups.  Check out the Virtual Earth Interactive SDK to see the latest details.