What many people have forgotten is the Gary Gygax was involved in the wargame hobby long before TSR and D&D. Gygax used to participate in wargame fanzines that were common in the era. They were one of the main ways gamers -- especially Diplomacy gamers communicated in the days of expensive long distance and no Internet. Starting in 1976, D&D articles by Gary Gygax and Len Lakofka (separately and together) started appearing in Lakofka's long running Diplomacy zine, Liasons Dangereuses. I saw one of these issues back then when someone had a copy of then current issue at an ancients game I was involved in.
I was surprised to discover that many issues of Liasons Dangereuses have been scanned and are available at the Postal Diplomacy Zine Archive as free PDFs. Warning: The site is a bit slow and the scans are not always the best (probably because the reproduction on the originals was not always that good). Here's a list of the issues I found with D&D articles of possible interest:
Liasons Dangereuses #70 – April 28, 1976 has a short article by Gary that talks about how D&D and the first two supplements did.
Liasons Dangereuses #72 – July 17, 1976 has "Women and Magic" by Gary and Len. This appears to be an early version of The Dragon article.
Liasons Dangereuses #73 – August 18, 1976 includes Expanding the combat tables in D&D and a long article about dungeon doors and some material from the Blackmoor campaign (I think).
Liasons Dangereuses #74 – September 27, 1976 has an article by Len and Gary "The Pryologist: A Study in Magic" -- a fire mage sub-class for D&D. Also "Capture and Bondage in D&D" -- rules for tying people up. Errata for some previous D&D articles.
Liasons Dangereuses #75 – November 10, 1976 has an article by Len and Gary on "Scrying in Dungeons & Dragons".
Liasons Dangereuses #76 – December 14, 1976 has an article by Gary and Len entitled "Dwarfs & Hobbits & Magic" with magic-using classes for dwarfs and hobbits.
Liasons Dangereuses #77 – January 26, 1977 has an unreadably light article on Metamorphosis Alpha and an article by Gary and Len on "Special Damage in Dungeons & Dragons".
Most of this material was new to me. I expect it will be to most OD&D players. Enjoy.