I have not put one up yet but when I do just got to http://mumble.sourceforge.net/ and download the client and then enter the address and password when prompted to add a server.
I am going to wait till closer till release to buy it. Plus I might see what bowzer and crews plans are for an incgamers mumble server too. If everyone is on that server I might not get one since we will have a location for everyone to reside.
The link I put up yesterday was for the /r/diablo server which is Reddits public diablo server. The guys were looking for a place to chat so I offered that one up.