gmoo
Linux client based on gtk+ supporting multiple worlds. It includes a builtin editor with syntax-highlighter and macro support, is almost completely customizable and includes MCP support.
LambdaMOO-Builder
GUI to develop text-based virtual realities with the LambdaMOO Server. For Win9x [no longer developed] and Java.
MacMOOSE
Macintosh client designed to aid MOO development in MOOs with MacMOOSE utils. Includes object browsers, WYSIWYG editing of verbs and properties, multiple connections and separate windows for help, sending MOOmail and the output of any command.
MOOps
Windows client featuring MCP 2.1 and ANSI support, editor with syntax highlighting, advanced history and paste and themes.
VMoo
Features an editor, visual who-listing (requires code installed in server), ANSI, MCP and TCL support, built-in MOO code parser, triggers and an integrated list of MOO servers.