Doom source port based on ZDoom...
A place where Doom level designers can post screenshots of their work-in-progress.
Forum dedicated to Doom and other game related stuff..
Rex's Doom site where you can find his levels, fiction and tutorials..
Site dedicated to Doom... news and forums, etc..
Doom Source Port
Tormentor's Doom related site.
Mr_Rocket's Doom related site.
Doom maps, utilities, somefin about voxels and a few hosted sites as well...
Karthik's site contains his Doom levels, art, movie info and much more...
Ismaele's site that contains his Doom maps and reviews of various maps.
Forum dedicated to Raven Software's games, especially Heretic II.