Here are some great Myst links:

Official Myst site: This is the official site of Myst, run by Cyan. It has some screenshots, sound clips, movies, and a FAQ section.

Official Riven site: Official Riven site, also by Cyan. Screenshots and other stuff.

Official realMyst site: Really well run website. The site is 1.2 MB large, but it is well worth it to wait for the loading. The layout is really awesome and has a Myst mood about it. You can see screenshots, view trailers (you should watch them, they're SO awesome), and get more info on realMYST.

Official Exile site: Run by Presto Studios, this is another great website, created to build hype about Exile. It does so successfully, with polls and contests. There is a gallery where you can view screenshots of the five new ages, a download area to get trailers and wallpaper, tons of links, and updated news on Exile. It has a good layout with a cool Flash intro.

Unofficial Riven Site: A site run by a fan. It is THE source of all Myst news. It has pages for Riven, realMYST, Exile, and the upcoming new Cyan game, codename "Mudpie". There is always updated new on the games, including release dates, new downloads, and other stuff. Not a particularly great layout, but the main thing at this site is the news. Also has hints for Riven.

Rivenguild : Place where Riven fans can gather. It has loads of screenshots for all the games and lots of extra downloads too (like a Riven font). There are boards and forums where fans can discuss the games, news on the new games, and alsosome creative puzzles based on the games.

Myst Gallery: Many gorgeous screenshots from the ages of Myst.