Homeland MUD is is open to all players and is located at http://www.homelandmud.org or via telnet at telnet://mud.homelandmud.org:6666
I've played on quite a few MUDs in my time. The most prominent one was Sojourn.
I've also co-founded a few MUDs. One that I did a lot of development for was at ExileMUD. And from time to time I still play there a bit, although I no longer do any active work there.
Since Exile I've moved on and founded HomelandMUD with a few of my old friends from ExileMUD. When we get to the point when we accept players we'll be located here. If you are interested in dropping by Homeland to see what we're up to, drop me a line in my journal and I'll get back to you with the current telnet address.