I meant deployments of software without an operating system other than Xen. Running an operating system on Xen means that you now have the Xen kernel and guest kernel that can have bugs.
I knew I must have been misunderstanding you. No, I am not aware of any.
Webservers can handle a big OS. The hardware is typically over specced as it is. You might find some utility in shrinking/streamlining the OS for embedded or mobile.