EUCALYPTUS - Elastic Utility Computing Architecture for Linking Your Programs To Useful Systems - is an open-source software infrastructure for implementing "cloud computing" on clusters. The current interface to EUCALYPTUS is compatible with Amazon's EC2 interface, but the infrastructure is designed to support multiple client-side interfaces. EUCALYPTUS is implemented using commonly-available Linux tools and basic Web-service technologies making it easy to install and maintain.
One way to go about democratising the "cloud". Some have cheekily aligned it with how current day linux came to form. A need for a free and hopefully standard platform. :-)
I don't know how useful it is, but I'm willing to give it eight points for the acronym alone.