First check out The Wolfenstein 3D Dome, The Diehard Wolfers' Forum, and The Wolf3D Haven Forums.

Wolfenstein 3D demos, abandoned/incomplete mods, authors' web pages, cheats, commentary, Easter eggs, forums, guides, mirror downloads, news, previews, programming code changes, reviews, saved games, screenshots, and videos:

Mods List With X

Total Conversions

Registered Wolfenstein 3D

Shareware Wolfenstein 3D

Registered Spear of Destiny

Shareware Spear of Destiny