iPath is providing an free and open platform for "case based collaboration", especially designed for medical applications (telemedicine, etc). The iPath-Server package provides a sort of medical BBS to discuss/consult cases online. Additional modules may be added.
I have been using their free web-based service for the past few years and found it very flexible and usable. It is also quite popular amongst many pathologists i know, who use the iPath server to collaborate on difficult Cytology/Histopathology cases.