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

Title, (# of Levels), by Author, Extra info
Amnesia, (3), by WolfAddict Software
The Armoury 1.0, (12), by Ian Brown
Battle Arena 2001, (1), by scooter_31210
Battle for New York Deluxe, (6), author unknown
Castle Morgmenistein, (17), by Joel Brown
Code of Arrogance, (7), author unknown
The Dark Fortress 2+, (7), by Masahiro Iwakura
Die Geringste Aussicht, (5), by M.J. Hunter
Doctor's Conference 1.0, (20), by Ian Brown
Final Solution 2, (12), by Pier Luigi Andreoni
It's only a dream, (6), by Pier Luigi Andreoni
Kamen Riderstein, (8), by Carlos Spesungel
Siberian Offensive, (20), by Ian Brown
The Tears of Dolly, Part 1 of "The Ambition of the Forth Reich Nazis" (10), by Masahiro Iwakura
Teletubbystein, (18), by scooter_31210, "Battle Arena 2001" included