Ubuntu Enterprise Cloud is the product, powered by Eucalyptus, that allows you to easily run your own Amazon-EC2-like private cloud. It’s a lot simpler than you’d think. More here
To deploy a minimal cloud infrastructure, you’ll need at least two dedicated systems. One will hold the cloud controller (clc), the cluster controller (cc), walrus (the S3-like storage service) and the storage controller (sc). This one needs fast disks and a reasonably fast processor.