OSCAR (Open Source Clinical Application and Resource) from McMaster University is a web-based EMR (electronic medical record) system developed for academic primary care clinics yet suitable in specialty and non-teaching practices. It integrates with Drugref to provide Canadian pharmacopea.
Proteus is a software technology that allows creating clinical executable decision support guidelines with little effort. There is a Proteus Intelligent Processes (PIP) Project Wiki available for the developers of the PIP open source project and others who are interested in learning more about Proteus. Proteus is composed of two sub-projects: Protean (Clinical Workflow Authoring Tool) and GreEd (Rule Authoring Tool).
iPath is providing a 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 are available.
Xebra is an open source, cross-platform, thin client and server for web-based distribution and clinical review of medical imaging results. Xebra is based on the latest open industry standards including JPEG2000, WADO and IHE XDS-I.