As it happens, I've recently been playing some Infocom text adventures. Guess what: Infocom were really rather good. Guess what else: there was one rather significant game they never released. And you can play some of it.
In a remarkable find by waxy.org (linked via the magics of QT3), amongst a complete archive of Infocom's work is the game Milliways: The Restaurant at the End of the Universe, the unreleased sequel to one of the most famous and adored IF games of all time, Adams' own Hitchhiker's Guide To The Galaxy. This was discovered on the somehow aquired "complete backup of Infocom's shared network drive from 1989."
So head over to Waxy for a stunningly detailed, beautifully researched piece, where Andy Baio pieces together the complete story of this game, via the remarkable archives of emails, design documents, and prototypes found on the drive. It's a huge piece of work, and tells a fascinating story spread over many years. Read Infocom's discussions of how to input multiple viewpoints in a text adventure, an outline for the puzzle structure, and the frustrations within the team as the project failed to come together. Quoth:
Look, we could quote the entire article here in celebration. But just go read it over there.
Most remarkably, the prototype is available as a Java app to play! It's a stub, a few rooms, but they're there and you can play them right now. Andy Baio, we salate you from atop a tall tower.