NetHack is a very elaborate, text mode, role playing adventure game. There have been many clones - Rogue, Moria, Angband, to name a few - and new graphical versions, such as Falcon's Eye, and the nethack QT, GNOME, and X11 (Xaw?) frontends. Its been ported to Linux, Dos, Windows, Amiga, Atari, OS/2, Mac, Psion and I think there are PalmPilot versions.
Get it from: http://www.nethack.org/
Nethack is one of my all-time favorite games, one I've been playing since 1200 baud was smokin' fast. -- Actor Wil Wheaton, http://www.wilwheaton.net
In short, NetHack 3.1.3 is the most elaborate role-playing environment you are ever likely to explore. This is a place to return again and again, each time for a different experience. You're really going to have to play it for a year or two and see for yourself. -- "Fatal Distractions" by David Gerrold
Thank you for the latest release of gradewrecker. My GPA just went in the corner and shot itself. -- USENET posting, author unknown
MS-DOS is, quite possibly, the worst text adventure game ever. -- signature seen on SlashDot.