Microsoft in Second Life
I've be a fan of Second Life for a while now (message me to exchange avatar IDs) and even have a relative who has worked in the SL world professionally, so it's great to see parts of Microsoft responding to the opportunity it presents.
There was recently a launch party in Second Life to unveil a second Microsoft island (and even a blimp!) dedicated to providing information, events, and of course interesting things such as puzzles to play with. You can visit http://visualstudioisland.com to sign up for Second Life or, if you already have SL, visit the island directly via secondlife://Microsoft/151/219/22.
Here's the island overview video (via http://micromiel.com/2007/05/09/visual-studio-in-second-life/):