Planetfall (1983) (Part 1, Part 2)
Sorcerer (1984)
The Hitchhiker’s Guide to the Galaxy (1984)
A Mind Forever Voyaging (1985)
Leather Goddesses of Phobos (1986)
Stationfall (1987)
Zork Zero: The Revenge of Megaboz (1988)
The entire collection:
archive.org/details/infocomcabinet
A weblog post about how this stuff entered the public domain:
ascii.textfiles.com/archives/4834