Doom programs

[Damien]

The doomsday engine [opengl]:

http://www.doomsdayhq.com/

extra files for doomsday [textures, models, gui, etc]:

http://files.dengine.net/index.php

Risen3d [d3d,opengl]:

http://www.risen3d.newdoom.com/

extra files for risen3d [textures, models, gui, etc]:

http://www.risen3d.newdoom.com/downloads.htm

Zdaemon, multiplayer doom [software, d3d]:

http://zdaemon.org/

Skulltag, custumised multiplayer doom [opengl, software]:

http://www.skulltag.com

zdoom, enhanced engine [software]:

http://www.zdoom.org

gzdoom, enhanced engine [opengl]:

http://www.grafzahl.drdteam.org

[Damien]

for lazy people [all the programs]:

http://www.iddqd.ru/newdoom.php

maps for you're program:

http://www.iddqd.ru/levels.php

mods [weapon replacements, tc's]:

http://www.iddqd.ru/mods.php