Doom II - Hell on Earth

Doom Reloaded
ShockWave version.
http://necromanthus.com/Games/ShockWave/doom.html

Doom2.net
Beginner guides, detailed game information, deathmatch tips, add-on levels and demos.
http://www.doom2.net/

Dr Deathmatch's Doom II Site
Wads, tips for setting up and playing deathmatch games, cheats and links.
http://users.mcmedia.com.au/~fpurcell/tom/doom2.htm

eLook
Summary of cheats codes for the GBA version.
http://www.elook.org/games/cheats/gba/269.shtml

id Software Doom II
Official site. Description, system requirements, technical support contacts and online purchasing.
http://www.idsoftware.com/games/doom/doom2/

My Doom II Page
Fan site with general information and a few wads.
http://www.angelfire.com/in/choose1/doom2.html

Sergeant Jms's Doom2
Includes a table with the shots necessary to kill each monster, the music for the levels in MIDI format, the ammo carrying capacity, weapons descriptions, items explanation and cheat codes.
http://www.angelfire.com/tx4/doom2/index.html

wackyhq
Home to DeCorEd, a lump editor for ZDoom, and Dark Forces Doom, a new total conversion project. Also has discussion forums, add-on reviews, demos and downloads.
http://www.wackyhq.com/