I just downloaded and read the latest GM's Monthly Miscellany: November 2016 and I'm impressed at what you get for the price of free. Sure, it's labeled Pathfinder, but GMs of any edition of D&D or its retroclones should find 10 pages or truly useful content.
I should grab all of the previous releases, as this is a sandbox GM's friend and then some. Print the pages out and just organize everything as needed: random tables, plot hooks and urban areas. Really, what more do you need to keep your players engaged when they step out of the dungeon?
Did I mention the price was free?
This month’s issue features:
-10 Cultists with Personality
-Suurin at a Glance (from Village Backdrop: Suurin)
-Tumblestone at a Glance (from Places of Power: Tumblestone Inn)
-20 Vile Things to Find in a Cultist’s Lair