Zork I (Microcomputer Version) by Infocom
The Hitchhiker's Guide to the Galaxy, by Steve Meretzky and Douglas Adams (Infocom)
Mainframe Version of Zork (Infocom)
A fast and compact library for writing text adventure games for the Z-machine running on 8-bit computers as well as other platforms.
Zork I (Microcomputer Version) (Solid-Gold Edition) by Infocom
Zork III (Infocom)
Zork II (Microcomputer Version) (Infocom)
A simple Z-Machine implementation in a single C file. Now with online multiplayer! :)
A Z-machine interpreter for the Commodore 64 and similar computers
Deadline by Marc Blank (Infocom)
Beyond Zork: The Coconut of Quendor by Brian Moriarty (Infocom)
The Restaurant at the End of the Universe (Incomplete, Unreleased) (Infocom)
Enchanter (Zork IV) by Marc Blank and Dave Lebling (Infocom)
A Mind Forever Voyaging, by Steve Meretzky (Infocom)
Stationfall, by Steve Meretzky (Infocom)