Dimdim is a Web Conferencing open source tool, still in Alpha-Version that seems to have a great future. There are a lot to say about it so I prefer to give directly the link ;)
By now it’s only work on IE and is full of bug but the idea is awesome. I guess it can be a good alternative to Breeze as they want it to be free.
Watch Dimdim demo.
Have more info.
Ahmet
Open Source Web Conferencing September 16th, 2006