Brass Lantern, the adventure game website.
This is the successor to Interactive Fiction section at About.com/The Mining Company.

Just Adventure + focuses on "all things adventure. Action/adventure, children's adventure, Mac adventure, console adventure, point-and-click adventure."

The Suite101.com page will provide you with news and information on Interactive Fiction.

The Frobozz Magic Co. is where "Zork's elite meets", and was once known as "The Great Underground Empire Home Page". Contains news, programs, solutions on items specifically relating to Zork.

The XYZZY News is an excellent newsletter dedicated to Interactive Fiction.

The Society for the Preservation of Adventure Games primarily reviews text adventures, but also provides directions on how to run and interact with text adventures.

The InfoDoc Project is the current home for PDF versions of Infocom's newsletters.

PDD's Adventure Page offers a useful collection of links tracing the history of text adventures.

Duncan Stevens has some reviews on Infocom and other Interactive Fiction games. (New location)

Zarf's Interactive Fiction page contains his award-winning text adventures, in Z-code and online Java format, and his reviews of commercial adventure games like Starship Titanic. The reviews are what I call "real world" reviews--honest and useful.

Matthew Murray also has many reviews, including almost all of Infocom's graphic and text adventures. These are also "real world" reviews. (New location.)

Other Interactive Fiction information:

GameSpot's review of The Masterpieces of Infocom.

"I Have No Words & I Must Design", an article on game design.

When Infocom and the Internet Oracle collide, a bit of humor.

Though the "Four Minds Forever Voyaging" article is available at the Unofficial Infocom Home Page, this website appears to also have some scans of drawings that accompanied the article. (Updated location)

Al Giovetti's website contains two noteworthy articles on Shay Addams, one of Interaction Fiction's early prominent figures. Shay had several magazine columns, the Questbusters and Simulations! newsletters, and published the Quest for Clues series of hint books.
"Whatever Happened to Shay Addams?" discusses Shay's whereabouts.
The History of Hint Books, Strategy Guides, and Cheat Codes that also contains information on Shay Addams.

Coming Attractions by Corona has details from 1996 about a possible movie based on the Zork Universe.