Microsoft SharedView for team collaboration
While searching for a team collaboration tool that would easily allow sharing my screen and documents with other team members, I came across Microsoft SharedView. This beta, released on May 2007, allows a "fast, easy way to share documents and screen views with small groups of friends or coworkers; anytime, anywhere."
The usability just is great, despite the poor performance and the lack of P2P support - something to be fixed for the RTM (hopelly). It is a small and simple tool that integrates with Windows Live Messenger making it really easy to use.
Check it out.