You should take a look at
EVO . It was developed by CalTech for use in the high-energy physics projects at CERN. It is a Java application,
no installation required, but works surprisingly well even with consumer webcams in mac and linux. You can use it for free by just registering and organizing a meeting in the 'universe' group, or you can request that your own organization is added (and still use it for free).
It has all necessary features: multiple video streams, collaborative white board, recording and replay, file storage,...
At particle physics labs around the world the meeting rooms are basically built around EVO, and polycom has virtually disappeared. It helps if you are close to one of those labs, or on an educational backbone.