Where are the D3 level editors posting links to their levels?
Where do I look for pilots deathmatching?
Is anyone making new robots. Is that possible yet?

Level Editor - http://www.descent2.de/
Levels - http://www.enspiar.com/dmdb/index.php
No new robots I think for D3.

Try Overload. Same devs as Descent but new game.

playoverload.com It just came out today.

DMDB is more D1/D2 focused. Try: https://sectorgame.com/d3

Yes new robots are possible in D3, but not many levels use them. There are a couple of single player levels that have custom robots, I forget which ones exactly. The Hyperspace levels (specifically Basewars and Silent Fury) also feature custom robots, though most of them are space ships.

Back in the day, PlanetDescent.com was a popular site to post files and missions for all of the Descent titles. You can use the Wayback Machine (archive.org) as a fairly organized means to view both single and multiplayer D3 missions:

https://web.archive.org/web/20100107142505/http://www.planetdescent.com:80/site/files/d3new/

However, you need to use http://www.dfiles.de to actually download the files that you find on the archived PlanetDescent.com site since they are almost all still available.

As an example, let's say you want to download 1001 Ways to Die by Starkiller on this page:

https://web.archive.org/web/20090308035342/http://www.planetdescent.com:80/site/files/d3new/index.asp?start=single

The FP link in the Download column does not work (it didn't even work in the final years of PlanetDescent.com). The DF link in the Download column typically points to some archived file that doesn't exist, in this case:

https://web.archive.org/web/20090308035342/http://www.dfiles.de/download/d3/missions/1001.zip

So remove everything in the DF link prior to "http://www.dfiles.de", and you should have a usable download link:

http://www.dfiles.de/download/d3/missions/1001.zip

It takes a little work, but there are over 600 missions available, so happy hunting!

Thanks folks. Its been a while.