The Interactive Fiction Archive, or IF Archive, is one of the older gaming traditions on the Internet. (Quick recap: Interactive fiction includes games or software in which the computer user takes an active (or, at least, participatory) role in determining the outcome of one or more characters.
The archive was first developed as a personal site by Volkier Blasius, a researcher at the Gesellschaft fuer Mathematik und Datenverarbeitung (GMD). Blasius had been collecting interactive fiction games from BBSes and newsgroups since the late 1980s, and took the next step of making them available across the Internet in 1997. They were for the most part unorganized, but over the years the collection grew and the site gained new administrators and helpers to keep the games in order.
The archive was not just limited to storing IF games, either. While many IF games were self-contained executables, there were also a large number of interpreters required to play games; programming frameworks and compilers to help developers more easily create new adventures; artwork for some of the more collectible games; manuals and FAQs; and, of course, the archive provided a walkthrough for almost every game in the set.
Finally in 2001, the site was moved to its current home at http://www.ifarchive.org. Today the Archive stands as the definitive center for Interactive Fiction fans to find a number of classic games, such as Zork, Hitchhiker's Guide to the Galaxy, Leather Goddesses of Phobos, and Adventure - in addition to a multitude of completely craptacular games that you will walk away from after 2 minutes, bitter and broken. It also contains articles on the history of Infocom and Level 9, instructions on using the on-site interpreters to create your own games, and even source code for a number of abandoned IF titles.
So if you're into IF, or want a neat place to get back in touch with your 80s self, the IF Archive is where it's at. Check it out.