This has been passed around a lot lately, but still an interesting read.
The development of the module Quagmire by Merle Rasmussen.
The article is less about module design than it is about commercial module development. It is insightful on how things were created in the heyday of TSR. Also if you look hard enough you can even see the seeds of TSR's eventual demise here.
I post this though because it is an interest footnote to me. I remember this adventure. I picked it up and completely gutted it because what I wanted was a swamp with a tower in it. All that hard work detailed above and I chucked it all!
This article did make me want to pull my old copy out, but I remembered that it was one of the many pre-2e materials I lost back in the mid-90s. Thankfully I do have the PDF. I might use it in my current game, but everything is so packed now I fear I will end up doing exactly what I did in the past; chuck the adventure and make it an interesting locale to stop over in.