Yuuguu 


Yuuguu is a free cross-platform (Java-based) screen-sharing application for Mac OS X and Windows that works impressively well (i.e., “just works”) and that ties easy conventional voice conferencing to the mix (they set up a conference bridge to which you can dial in to at moderate rates – no Portuguese numbers, though).

The coolest thing is that participants can join a conference using nothing more than a browser and a Flash client.