Infocom adventure games are some of the grand-daddy's of text adventures. Zork is by far the most well known, but also pretty infamous are Hitchhiker's Guide to the Galaxy, Leather Godesses' of Phobos and A Mind Forever Voyaging. As a warm-up, I'd recommend Moonmist. It's a mystery game listed as a "Beginner" game, and is great for introducing elements of the Infocom system. The feelies are available to view here: ht…
Trinity is another good one. As is The Lurking Horror--set at a thinly-veiled MIT campus where many of the authors were from.