http://www.doomchronicles.com/index.php At this site is a demo, and information on the best game mod I have ever played for any game. It is the DOOM 3 mod that goes by the name of DoomChronicles.

DoomChronicles most noticable change to the game is, of course, the new levels. But, even more so, the new weapon mods. The weapons now have multiple fire modes which are all great. The particle effects are improved, and the new sounds for them are awesome. You can even throw flares in dark corners, before you make a mistake, and get face to face with an imp. Another noticable change is the imp and spectre. The new imp is like a ghost, glowing orange like its own fireball. And it even throws it's fireballs faster. Good news is you can dodge them right back at the imp with a gravity gun. The mods version, not ID Software's. Guess that gun is getting popular. You can even toss smaller enemies around, including zombies. The spectre is crystal clear like water. But, I would like to see him more as a shadow spectre. I saw some screenshots of the later Hell levels. And, they remind me a lot of the classic games. With hanging corpses, tons of blood, guts, bones, fortresses of evil, and tons of fire glowing pentagrams.

Here are some other DOOM 3 mods I have my eye one:

http://www.planetdoom.com/edgeofchaos/ Edge of Chaos - A full conversion for Hexen!!

http://www.mindplaces.com/darkmod/ The Dark Mod- DOOM 3's version of the Thief 3 game. I dont know if you play a thief, though.

http://www.doomworld.com/unholy/future/ Phobos - a continuation of DOOM 3?

http://www.planetdoom.com/optd/ Operation Take Down - No info yet

http://www.planetdoom.com/d3f/info.html DOOM 3's version of TFC

http://www.d3jedi.com/ DOOM 3 Jedi - A Star Wars Jedi game for DOOM 3

http://www.planetdoom.com/theevil/story.htm The Evil - Massive worlwide zombie infection

http://recalltohell.d3files.com/rth_eng/news.htm Recall to Hell - A DOOM 3 continuation?

http://www.planetdoom.com/zombie/ Zombie Brain Repository - Another zombie mod

http://www.facinghell.com/?cid=faq#1.1 Facing HELL - A Doom 3 3rd party add-on

http://cdoom.d3files.com/index.php?page=news Classic DOOM for DOOM 3 - obvious

Still waiting for an ALIENS or Predator based Mod.