Mudlet - Mudlet is a freshly-minted MUD client, designed to take mudding to a new level.
Lectrote - A portable Interactive Fiction games interpreter application
MUSHclient - MUSHclient - a 32-bit MU* client
CMUD - Are you tired of the constant grind of the graphical MMO games?
Windows Frotz - Windows Frotz is an interpreter that can play all the old Infocom text adventures.
TinTin++ - TinTin++, aka tt++, is a free MUD client for Mac OS X, Linux, and Windows.