SMAUG
The home of the original SMAUG codebase. Without them, there's a good chance none of us would even be here right now :)

SmaugWizard Home Page [Defunct link removed]
The homepage for the SmaugWiz codebase and the area conversion program for use with it.

The Sourcery
A site with lots of useful information on MUD development and administration. Also has some interesting historical data.