From the update:
The second of the core rulebooks for Adventures Dark and Deep™ is now available! The Game Masters Toolkit gives a ton of tools that the game master can use to help run his games, and almost everything is generic enough to be applicable to any sort of OSR-compatible rules. Here are just a few highlights:
Guidelines on what sort of races (sub-races, underground races, etc.) can be included in a campaign, and the potential impact of the choices you make
NPC generation (including two big tables of physical and personality traits to give NPCs a little color quickly)
Dungeons, wilderness, and underwater environments and hazards (including pits, weather, privation, swimming, etc.)
Non-melee combat-- tournaments, hunting, etc.
Rules for creating detailed treasure hoards that are more than just coins and gems
Ships and waterborne travel
Notes on creating a campaign setting; bottom-up vs. top-down philosophy; classical, underground, and Mythos-inspired campaigns; religions and deities (including a complete sample religion from history-- the Norse); the various other planes of existence (including variant systems and cosmologies)
Notes on creating adventures; storylines vs. sandboxes, wilderness adventures, and urban adventures; and tips on handling clues for players, meta-knowledge, and problem players
A comprehensive listing of magic items, including rules for intelligent items, selling magic items, etc.
An appendix with more than 80 random tables for the game master to use as inspiration, to fill in details, provide quick answers to common questions, etc. Everything from "What does that elf have?" to "What's on that evil altar?" to "What is that mountebank doing here?" to "Why are those humanoids raiding the village?" to "What happened to me in the tavern last night?" to "What is the city watch doing here?"
And of course tons more stuff
The rules are being released under the OGL, and as usual all hard copies of the book come with a complementary pdf copy. The whole is copiously illustrated, and features a cover by awesome gaming artist Christian N. St. Pierre.