I've mentionedbefore that I have a predilection for buying other peoples' RPG collections. Since then, I've acquired one or two more collections, and lost a whole lot of space en mi casa. As I've gone through these collections, I've found that my favorite part of these endeavors is not so much the box sets and the books, as it is the ephemera that accumulates over a lifetime of gaming.
First off, maybe it's just the subset of people I got these from, but every single one of them had at least one bootlegged copy of a book, printed out on several hundred pages of loose paper, holes punched and inserted into binders. Someone in our group does that, but I always figured it was just him. Apparently, pirating was a well established form of gaming before the internet made it popular. Hipster pirates, if you will.
Secondly, I now am the proud owner of enough pregenerated NPCs to last a lifetime of gaming. Going through them was like getting a glimpse of their previous owners' gamer souls, if you please. One person was obviously a huge fan of Wild Mages, as 95% of the characters were either Wild Mages, or dual/multi classed, with one of the classes being a Wild Mage. I remember reading about that class in the 2e Tome of Magic and thinking, "Who would be crazy enough to play that?"
Now I know.
Another collection had two copies of the Starship Troopers Bookshelf game, which had been owned by the person's uncle (who apparently got him started in gaming). This uncle was, according to the label stuck on the inside of each cover, retired from the United States Marine Corps, and he took his gaming VERY seriously. There was a handwritten note that he had (I imagine) meant to send out, but never gotten around to, where he offered criticisms of some of the finer points of the game, and offered suggestions on how it could be better. Also in the book was his own modification for the game, taking the whole "Science Fiction" thing out of the game, and turning it into a way for him to reenact the battles he himself had fought.
The real fun, though, is the campaign material. One of the collections netted me an entire megadungeon, painstakingly drawn out on graph paper, and slipped inside clear plastic pockets. This person had connected a grease pencil to a string, and tied it to the binder, and was using it to mark the party's progress through the dungeon. The seven levels and the exterior were detailed on approximately 30 or 40 pages, initially typed on a typewriter, and then annotated in pen. There were even random encounter tables in the back, with the stats of the monsters included!
All kinds of stuff is out there, I hit Craigslist every couple of days, looking for my next big score. I should call the History Channel and see if they have room in their lineup for a guy who looks for D&D products on Craigslist!