business of software conference

What software can I use to video conference 5 locations?

I need to have 5 webcams with voice in a video call (perhaps the need for more later), similar to the way sites like stickam work. This is business related and must be private rooms. It also needs to be easy to use as some users are novices. What software can I use to achieve this? Free is preferable.
Unfortunately ooVoo will only do up to 3 video users unless you pay for the pro version on all the clients.

try oovoo

http://www.oovoo.com/

Jason Fried Talk @ the Business of Software Conference