Mudlet is a modern client which works on PC, Mac, and Linux systems. It uses LUA for scripting and has a very powerful mapping utility. It is probably the best choice for a new player!
Check out the Wiki section for Mudlet to find helpful Mudlet configuration/tips for Dune including chat capture windows and information on connecting to Dune securely.
TinTin++ - TinTin has been around a long, long time, and it's one of the the most flexible MUD clients around. It's free and runs on anything *nix, Macs and Windows.
Check out the Wiki section for TinTin++ to find helpful TinTin tips/configuration for Dune including information on connecting to Dune securely with TinTin and use GMCP.
BeipMU - a MU* client that provides an assortment of features beyond simple telnet. Features: SSL/TLS, IPv6 Macros, Triggers, Aliases, Spell Check, Maps, Stats, Notes, Spawns. (Free/Open source)
MUSHclient - A powerful client with many scripting languages, active boards, and good support. The client is also freeware, which is a plus. (Freeware)
CMud - The new and improved zMud, CMUD is faster and offers a variety of new features. Unfortunately retired from development, however you are also likely to find many people on the MUD who can help you set up. (Free 30 day trial).
Check out the Wiki section for CMUD to find helpful CMUD configuration/tips for Dune contributed by players.
zMud - Retired from development, this client was the staple for many of the players here on Dune. The last version is still usable for some! (Free 30 day trial)
MudWalker - Last release was around 2005. Some features are: Compact connection windows that use no unnecessary screen space, supports Telnet, MCP, ANSI color, and TWin protocols, full support for extended character sets, including Unicode and Windows encodings, scripting using the Lua programming language, automatic login scripts with support for multiple accounts, etc.
Atlantis - Atlantis is a client specifically designed to aid in playing those type of games. It is designed from the ground up entirely in Cocoa, and integrates with system services — such as the Mac OS X spellchecker — as much as possible.
Blightmud - Blightmud is a Linux/MacOS terminal MUD Client written in Rust. Triggers, aliases, and other scripts are written in Lua (similar to Mudlet). It supports TLS (including certificate validation) and has a “split screen” mode for easy reading of your scrollback. It is actively developed and has many features! Give it a shot and ask Paradox in game if you need any help.
TinyFugue - TinyFugue is a Unix MUD Client with a minimal interface and incredibly powerful scripting support. It's command line based (no GUI) making it excellent to run on a headless server, or as a background process (see screen utility). A third-party patch is available to add Python scripting language support. Probably not the best choice for someone new to MUDing, excellent for anyone with programming kung-fu.
Irssi is first of all a text-based IRC client for Unix-like systems, but can also run command-line programs such as telnet in the same session. It is script-able with Perl, and is available for Cygwin. In conjunction with BitlBee you may also keep track of messages over other instant messaging protocols with this program.