Dimdim is a startup who promise easy conferencing platform without need to install additional desktop client, looking for hosting, anything. All you need is a browser :-). You can create online conference, share your desktop, voice and video (imho for for sharing your desktop is some plugin needed to install).
It's been a while Dimdim successfully integrates in Moodle, now the company releases new version, it's out of beta and will be releasing its source codes under GPL3 license.
Basic, free version, allows 20 attendees in the room, but if you need create bigger conferences you have to pay.
I saw some captures from Dimdim usage, it is looking very promising. Maybe it is a time to check it too, it is on my to-do list for a long time.
Some goodies here, if you will sign-up through this Techcrunch arcticle you may be awarded with Pro version (worth $99 annually, room for 100 attendees etc) for free :-).
Did you try Dimdim in Moodle? What's your experience?