The University of Pennsylvania, in partnership with IBM has created a very large scale, distributed, data storage and transfer system. The details can be found here.
This system is not, in itself, open source or free, it is built on open source components and provides some interesting ideas for the directions that health care IT might be going in:

VPN’s and Grids.

While the net outcome of this project has resulted in a commerical spinoff, there are several aspects worthy of consideration:

#1 – Extensive use of linux

#2 – An example of grid computing in action

#3 – The use of VPN technology and encryption to build a secure, networked system that has no security impact on the host, health care systems network (this is from a security perspective, performance is another thing 😉