Tim Freeman posted a piece of one of the emails sent out by XenSource's Ewan Mellor, where he gave a run down of old and upcoming Xen Management interfaces.  Tim also listed a number of other management interfaces that aren't released with Xen, and has accumulated quite a list.

• xend-http-server: Very old and totally broken HTML interface and legacy, generally working SXP-based interface, on port 8000.
• xend-unix-server: Ditto, using a unix domain socket.
• xend-unix-xmlrpc-server: Legacy XML-RPC server, over HTTP/unix, the recommended way to access Xend in 3.0.4.
• xend-tcp-xmlrpc-server: Ditto, over TCP, on port 8006.
• xen-api-server: All new, all shiny Xen-API interface, available in preview form now, and landing for 3.0.5.

And Tim's current list includes:

• Virtual Workspace Service
• XenMan
• DTC-Xen
• Enomalism
• xen-shell
• Argo
• Xen + CIM
• openQRM
• MLN
• Xenmanager
• using SystemImager
• XenSource Products
• Virtual Iron
• Cassatt
• BixData
• Egenera
• HyperVM
• ToutVirtual
• Enigmatic
• Xen and Moab Workload Manager
• IBM Director

Keep up to date with the latest list, here, on Tim's Web site - GridVM.org.  Thanks for the information Tim!