The interwebs are abuzz with news of OpenStack - an open source cloud stack initiative incorporating NASA's Nebula, Rackspace code, and the work of many others.
Here are three helpful links if you want to learn more:
My take: The "Cloud" continues as an area of rapid, relentless innovation. The cloud market is exploding with new approaches, technologies, architectures, etc... A credible open source effort to develop open technologies for enterprise and government cloud deployments will help foster competition and fight vendor lock-in for this market. Innovation is occurring too rapidly for standards efforts to make sense yet, but open work will lead to good results in interoperability as well.
update: this article discusses NASA's decision to drop Eucalyptus from Nebula. it provides an interesting insight about commercializing open source. (and, en passant, a discussion of Eucalyptus scalability). see: http://www.theregister.co.uk/2010/07/20/why_nasa_is_dropping_eucalyptus_from_its_nebula_cloud/
update 2: more from Andy Oram at O'Reilly Community: http://broadcast.oreilly.com/2010/07/openstack-offered-as-rackspace.html
update 3: Fred Trotter note the applicability of Open Stack to HealthCare IT: