Joe Bloch, aka the Greyhawk Grognard, has just launched a Kickstarter funding event for Adventures Dark and Deep, a Curious Volume of Forgotten Lore. This product is a supplement for 1st edition and OSR products, adding new classes, spells, monsters, a streamlined combat system, and other features.
If you haven't seen Joe's material, painstakingly and lovingly coaxed out of dozens of sources on Gary Gygax's intentions for the advancement of Advanced Dungeons and Dragons, you are missing a distinctly Gygaxian expansion and clarification of the game. As Joe puts it, it's his attempt to render the AD&D 2nd edition Gygax would have written.
I support this on Kickstarter and I encourage you to do so as well.