GNOME-Mud: GTK client, with most standard features. Allows Python scripting.
Kmud: KDE client, with most standard features.
Mcl: Console client, with most standard features. Allows Perl and Python scripting.
Mmucl: Tcl/Tk client with a console version. Provides Tcl based scripting and basic features.
MudTelnet: Console client using the real telnet protocol. Allows triggers and scripting by perl, C, C++, and shell.
Powwow: Console client with most standard features.
RMC: GTK client, with basic features. Aims to be easy to use.
SClient: GTK client, with most standard features.
TinyFugue: Portable console client with most standard features. Has some MOO specific support.
Xpertmud: KDE client, with basic features and plugins. Allows Perl, Python and Ruby scripting.
Ymusk: Tk mush client written in perl.