I've played way too much DOOM, I still have "D!MATCH" (D! doom interface and 150 deathmatch levels) and "The ultimate doom add on collection for Doom and Doom II" CD's. Along with the games of course. I got a lot of extra Quake levels too, "Malice, 23rd century ultraconversion" and "Dark Hour" for a start.
I still go back to them every now and then (on various platforms) and now I've looked at that article I think I'm gonna have to do it again, dammit, that's another week gone and it's all your fault.
The only question is which wad to load up.... hmm.... only a few hundred thousand to choose from.