Not sure of others but I am used to Rhubcom's appliance for over an year. There is no monthly fees, you own it, you control it. RHUB delivers advanced Web conferencing software for PC and Mac in a secured appliance. Yeah if you are looking for freewares then go for skype , netmeeting etc but its like compromising with information security and lot many bugs with session breakdowns are common. So for professional purposes must opt for quality solution.