There are a couple of great tools I use which may help others;
DimDim : Free, No Install, Registration required to “Host”, Voice, Video (20 people) & Desktop Sharing.
TokBox : Free, No Install, Registration required to “Host”, Voice & Video (20 people) but no Desktop Sharing.
TeamViewer : Free, Install Required, No Registration Required, Voice & Video (1-to-1).
Clearly DimDim is the winner at the moment, I’ll update if / when this changes! 🙂