MUD's

MUD's (Multi User Dungeons) are games like ADandD, exept that you play with a computer. You telnet to a MUD's address & then you can fight against/with & talk to other players in real time. There are different types of mud ranging from Fantasy->Si-Fi (play Star Wars, Cyberpunk, DiscWorld, WOT & many other orginal ideas) and range from hack 'n slash MUD's where you can kill other players, to mud based around roleplay and talking, and everthing inbetween & beyond.
Have a look at the MUD FAQ for futher info

LINKS

Big List of Muds containing descriptions and addresses.