Contrary to what some people might have thought, the CodeWalrus Minecraft server, located at
http://mc.codewalr.us , is still in operation. It just has terrible uptime.

The only catch is that now that Juju has moved, if the server goes offline then it is only re-opened on-demand, meaning that you have to bug
@Juju about it. Also, it requires a Minecraft version from the early 70's and it's world-edit-based creative rather than survival, but our affiliate
BosaikNet runs a survival server for those who prefers that.