I've been playing Doom practically ever since it came out (I vaguely remember the computer-wall/green armor lift accident in E1M3 - version 1.1 or so). Soon after I saw it I wanted to make levels for it.. Well, being the kid that I was (I must've been what, 9?), I started drawing a bunch on random sheets of paper... some good ideas, some bad. (I can say today that there were more bad than good. :P )
After a while, I discovered actual map editors - EdMap, DCK and so on. I settled on DeeP (at the time I would've never thought the shareware limit would even be reached, much less such a big limitation ;).
When I got my own computer which could run Doom (a Zenith 486, inherited from a brother who outgrew it ;), I was also old enough to know what makes a good Doom level. (At this time I "outgrew" Doom, moving on to Doom 2.) Started making good levels...
Well, enough boring stories.. on to the Good Stuff!
Doom is set in the future: scientists are working on a top-secret transporter technology which instantly moves matter from one location to another. Then something goes wrong - terribly wrong - monsters are teleporting in left and right, and are flooding the moon base! Many of your comrades have already died at the hands of these hellspawn, and you're one of the few remaining. Blast your way through the moon base and save the project.
But it doesn't stop there. Nothing can stop them, they keep pouring in. You escape to Phobos then Deimos - Mars' moons - screw the project, now you're just trying to get your ass out alive! You descend to the surface - the bastards are everywhere! Your only hope is to destroy them all.
In the end, you do hop on a portal to Earth.
Doom 2 continues where Doom left off: that elipsis ("...") at the end of the third episode had to mean something, right? ;) Indeed, Hell found its way to Mother Earth herself. Battle through cities-turned-demonic-worship-temples to save Earth!
Final Doom is Doom 2-based. It consists of two brand-new IWADs, TNT and Plutonia (and, I think the Master Levels). 64 more levels of mayhem! Blame it on Team TNT. :)
My collection of Doom and Doom 2 (mostly the latter) levels. Some finished, some test and example levels, and many incomplete. ;)