intin is the most popular Linux/Unix client for MUDs . What Tintin offers over telnet is the ability to have certain things on the mud be performed automatically by Tintin (scripting), split screening (input on the bottom of the screen, MUD on the top), and command aliasing.
To download the most recent version of tintin++ click here
Once you have Tintin up and running, you will want to take a look at the Tintin Help Guide. After using tintin, you may want to see a nice little file of the applications of commands, go here: Tintin Commands.