John Romero is virtually synonymous with Doom as one of its key developers, but he never made a map for it after 1995. Quake, and eventually his other studios, took over after that. However, he's finally coming home to roost: Romero has released an add-on map for the original Doom, "Tech Gone Bad," that reimagines the Phobos Anomaly at the end of Episode 1. That's bound to whet your appetite if you're a veteran gamer. He's not only intimately familiar with Doom, he's approaching it with 21 years of additional experience under his belt -- as early reactions attest, this is probably much better than the homebrew maps that you saw two decades ago.
You'll need to brush up on running third-party maps, since Doom hails from the old days of command line modes. However, you might have a good reason to dust off those old skills. Romero describes this as a "warm-up," so don't be shocked if he makes further maps for Doom, Doom II or something else entirely. Let's hope he gives the new Doom a shot, whether it's the built-in easy level editor or something more advanced -- it'd be interesting to see what he could do when melding old-school gameplay with modern technology.