The Grey Grimoire is a pdf fanzine produced by a number of well-known names in the Greyhawk community.
It clocks in at 31 pages, and has 10 articles, ranging from a new monster, the Darkened Depths Eel, to historical information on the Oeridian Migrations. Everything seems to be statted for 5th edition, but a lot of the material seems to be pure lore, so is system agnostic.
All in all a fine work, and it’s free! You can find the current issue here (and the same site has the first four issues as well).
