There have been a few shared desktop applications available for a while. Sadly they're either slow or expensive (or both) and not viable for small ad hoc project teams.

Well, help is at hand. Codename "Tahiti" from Microsoft has just gone into pre-beta and is open to all (provided you're quick) for free. The official beta is scheduled for late May and more people will be able to join up to play.

Teams of up to 15 people may use it to share applications like Notepad or Word (and if you have change tracking on in Word then Tahiti records who changed what) as well as screenshots that participants can see but not change.

Anyone with a LiveID can join into a session, but the organizer can control who is invited and who actually gets access to the session so you don't have to worry about eavesdroppers. Unhelpful attendees can also be forcibly ejected at any time (and blocked from trying to return!)