It's been a long time between posts about Doom 3, but the modding community is still kicking alone, and the Last Man Standing co-operative mod is one of the front runners. They've announced version 4 is coming soon and will have some cool features:

As always there are a lot of exciting things going on at Last Man Standing Co-op! We are moving forward to the 4.0 release and we have a lot of neat goodies for you. Hobbes has been really working hard and doing a great job on bug fixing and adding new features. Also he made LMS 4.0 compatible with the Doom 3 patch 1.3.1! There are way too many fixes and features to list in this news post but here are some of my favorites:
* Lots of lag tweaks! Hell has been optimized and is running with a huge FPS improvement
* Ragdoll fixes. Now zombies ragdoll instead of disintegrating
* The in game scoreboard now shows the high scores so that players know how many points they need to reach the top 10 list
* A new scoring system has been added where the score for killing a monster is multiplied by the skill level to give those players playing on high skill levels more points
* Boss health is displayed

There's also going to be a bunch of new maps. If you've still got Doom 3 kicking around and fancy some co-op, might be worth dusting it off in preparation.