Progress Quest

Players build their character from a ninety-pound level one teenager, to a warrior, well able to snuff out the lives of a barnload of bugbears without need of so much as a lunch break. (Windows)
http://www.progressquest.com/

K2W RPG

A collection of open source client, server, and editor you can use to build and run your own online RPG.
http://www.k2wrpg.org/

DimensioneX Multiplayer Adventure Development Kit

Offers a freeware Java software capable of building and running multiplayer adventure games, playable with any browser. Several multiplayer games are available for free as a demo.
http://www.dimensionex.net/en/

Orion CRPG Game Suite

Create and play Dungeons and Dragons style text adventures for Windows.
http://www.geocities.com/ravenskulluk/OrionGS.html

Exult

Version of Ultima VII for Unix, Windows, Mac, BeOS.
http://exult.sourceforge.net/

Faldon

Online role playing game for Windows with equipment, items, magic, skills, levels, experience, and a real-time battle system.
http://www.illusorystudios.com/faldon/

Lost Hero

A classic-style Java-based game, with information and download.
http://losthero.sourceforge.net/

Umbra

Free humanity in a randomly-generated world. (Requires Python)
http://kuoi.asui.uidaho.edu/~kamikaze/Umbra/

Dungeon Game

3D dungeon crawler for Windows or Linux.
http://tempusmud.com/~jwatson/sdl-dg/

IRE

User-editable clone of Ultima 6 for DOS, Windows, BeOS, or Linux. (Open Source, BSD)
http://ire.sourceforge.net/

Dark Ages II

Medieval DOS game in which the hero must defeat a wizard and avenge his family's death.
http://dk-software.com/index2.html

Hadinshu

Provides information, media, guides, and development information on Hadinshu, a fan game similar to Final Fantasy.
http://www.freewebs.com/dark_paladin_cecil/

Wheel Of Time - Light And Shadow

An online virtual community in Java based on Robert Jordan's Wheel of Time books. [Open Source, GPL]
http://wotlas.sourceforge.net

Zelda Classic

Replica for Windows of NES version of The Legend of Zelda. Includes development notes, download, enemy list, walkthroughs, and FAQ.
http://www.zeldaclassic.com

Palace of the Tragic Prince

Provides a download of the game called "Heart of Steel", information, screenshots, and links.
http://www.freewebs.com/tragicprince/

Crisis Wolverine

Provides a download of "Crisis Wolverine". Includes information, news, and media.
http://www-personal.umich.edu/~ebaraf/Crisis%20Wolverine%20Insurrection%20Green.html

Fanwor

Describes Fantastic World style game for Atari and Linux, with download.
http://www.uni-ulm.de/~s_thuth/ix/fanwor_en.html