Another thing Second Life got very right was the use of spatialized voice chat. That means you're not just able to look out of your avatars eyes and see who's i

Another thing Second Life got very right was the use of spatialized voice chat. That means you're not just able to look out of your avatars eyes and see who's in the room and who is currently talking (WebEx or Skype can do those), but you hear with your avatars ears too - so you can tell which direction the voice is coming from, which is very powerful when mixed with an avatar. You can tell speakers apart better and you can even turn your virtual head when you hear someone speaking from one direction and focus on them. It's a much more natural way of communicating than just mixing all the audio inputs together, and allowed me to associate voices with people (and their avatars) much better. Plus, if you can be bothered to learn the editor, you have some pretty powerful collaborative 3D modeling tools right there with you, which are handy for quick illustrations.