Although Ubuntu is generally regarded as a desktop Linux distribution, the sever variant is becoming increasingly popular in the cloud. It is silently infiltrating server rooms and gaining traction in enterprise environments. A recent survey published by Canonical provides some insight into adoption trends of Ubuntu on production servers.
As Ubuntu's presence in the server space grows, it is showing up in some unexpected places. Weta Digital, the New Zealand company that did the special effects for Lord of the Rings and some of the 3D rendering for Avatar, reportedly runs Ubuntu on its 35,000-core render farm and virtually all of its desktop computers. The Wikimedia Foundation, the organization behind the popular Wikipedia website, rolled out Ubuntu on 400 of its servers in 2008. We even use Ubuntu ourselves on several of the key servers that power the Ars Orbiting HQ.