There are all sorts of good random tables out there, from countless different systems, along with all sorts of lists available with adventure hooks, dungeon dressing, traps, etc.
But none of these tools are actually useful unless you can use them on the table. So, I did just that, and started printing out pages from various .pdfs I have to put in one big binder of DM resources!
Here is the cover
Some Palace of the Vampire Queen style empty dungeon keys, in case I need to make something in a hurry/want to make a reference key for an adventure.
Krevborna's Gothic Adventure Generator, in case I want to run something more role-play heavy than a dungeon crawl.
I have a couple pages from my house rules, not the whole document, but stuff like a list of magic items and this handy generic monster table.
For outdoor adventuring I printed out a few pages of lay of the land tables from Hubris.
I also put in most of the appendixes from the AD&D Dungeon Master's Guide.
I also have 2 pages from the Oldskull 1000 Rooms of Chaos, some pages from Zweihander and Shadow of the Demon Lord, 2 levels of Rak-Arnesh, and the mutation tables from Hubris.