OpenXenManager , which is part of the XenseMaking project is a Open Source clone of Citrix XenCenter which works on Linux, BSD, Windows and MacOSX. While Citrix XenCenter only runs on Windows, OpenXenManager basically runs on every platform which is capable of running python. The product is currently in alpha stage.
OpenXenManager is written in python with pygtk and a and gtk-vnc (or vncviewer). It provides the ability to monitor virtual machines, access virtual machine consoles, perform allowed operations (start, stop, suspend, reboot…), create virtual machines, and more.