you are likely to be eaten by a grue
The Interactive Fiction Archive features a vast collection of shareware and public domain text adventure games. I used to spend many hours pondering such games on the onld TRS-80s back in high school.
One day shy of a year ago, I mentioned the Java version of the Hitchhiker's Guide to the Galaxy text adventure. The good people at Infocom have also made the first three versions of my personal favorite text adventure game, Zork, available for free download. w00t!
(via Long Story, Short Pier)