HowtoForge has revised their “Perfect Xen”-guide to use Xen 3.0 on Debian Sarge.
Enjoy it here
I will use Debain Sarge for both the host OS (dom0) and the guest OS (domU). In an additional section at the end I will also show how to create a virtual local network with virtual machines, with dom0 being the router.
This howto is meant as a practical guide; it does not cover the theoretical backgrounds. They are treated in a lot of other documents in the web.