This guide is a brief reference for some of the commands useful for building rooms. Note that your character needs special permission to use these commands, unauthorized use will give a "Permission Denied" error.
Currently (10 Apr 2007) all players by default will have the necessary permissions. This will change once the builder "mini-beta" test phase is complete. For normal game play, most players will have much more limited access to the map editor - it will be possible to create/design your own rooms, but the effects won't be instantaneous. And you will need to go to a special location and/or vendor in order to use the editor.