When it comes to articles related to D&D history, not all these sources agree on all points (of course), but together they are a fairly rich resource.
There are a couple very interesting sources on proto-D&D. The tradition of the "free kriegspiel" is one precursor that can be googled fairly easily. A direct precursor can be found in Dave Wesely's "Braunstein" game. At the Acaeum, Wesely himself has commented a bit about his contribution, and there are some good links at the Wikipedia page on Wesely. This link is worth looking at, as is this interview with Dave Arneson, which also mentions Wesely and Braunstein. Ewilen also has a summary, as well as other relevant links and comments in his livejournal archives.
Another precursor in the free kriegspiel tradition appears to be Mike Korns's "Modern War in Miniature." Wilf Bakchaus ("Chivalry and Sorcery, 1976) talks about Korns's game in this short but interesting piece at "Places to Go, People to Be."
Historical Notes and Anecdotes
Some of the players from the early days of D&D have talked about their memories of game play on various forums. Greg Svenson (gsvenson) and Bob Meyer (robertthebald), two of Dave Arneson's players from the early days talk about Blackmoor in this thread. Svenson adds additional thoughts on Blackmoor here and there.
Mike Mornard, another player from D&D's early years (from both Gygax's and Arneson's games), is a fairly prolific poster on RPG.net and other message boards. Here are a handful of his anecdotes of historical interest:
1. on henchmen, strongholds, the D&D endgame
2. on learning the rules through exploration and again
3. on the use of minis in D&D and again
4. on XP, treasure, and wandering monsters.
Actual Play Reports
Greg Svenson also has a D&D page, which is home to his "The First Dungeon Adventure" actual play report. He has another actual play report here, this time with orcs.
At least one of Gary Gygax's actual play reports is online and can be found at this board.
Here are the main reports on Gary Gygax's house rules: version 1 was compiled by R. Fisher and version 2 is a very quick post by Gary on the topic (his username at ENWorld was "col_pladoh").
For comparison purposes, here's an RPG.net account of a Dave Arneson run D&D game and his house rules.
For more old school house rules, here's a copy of The Perrin Conventions on the OD&D boards.
Classic D&D References
Here's our current rules reference document (pdf) for Basic/Expert D&D play. It's primarily for use with the Moldvay/Cook Basic and Expert sets, but some of the pieces are from Mentzer's edition and the Rules Cyclopedia, from the Holmes Basic set, and from the OD&D books. The document is originally based on Robert Fisher's Classic D&D quickref, with a generous helping from Philotomy's OD&D musings, especially the combat sequence notes he drew up based on Swords & Spells.
Robert Fisher's Classic D&D page is full of great thoughts and ideas that influenced the approach I took with our D&D game last fall. His quickref was the basis for my own rules reference sheet, and I found his articles On thief skills in classic D&D and I used to think... both interesting and useful early on.
I partially hijacked one of Judd's livejournal posts a few weeks ago and I don't think I linked to it here. So now I am. Just some thoughts on why some folks might not agree that 4e really nails the heart of what D&D is. I should probably add that I don't have any particular take on 4e myself yet: I haven't even read it yet and I don't pretend to have an intelligent opinion on it. My thoughts in this post have more bearing on traditional D&D. Here's the discussion for reference. My posts are fairly long and scattered throughout, but they're concentrated in two blocks: here and here. I also touched on some thoughts about the rhythm of D&D play in a short comment in an RPGSite post a couple years ago.
Wired posted an article with a number of interesting historical bits and pieces, and there are some interesting bits in this Believer article, though to my mind, it's a bit spottier.
This is a necessarily partial and limited overview, entirely rehashed and without anything substantially new in it. But you still might find something useful in there if you're interested in D&D.
Recently, Justin Alexander posted a collection of "Accumulated Lore." D&D history gets some attention here, though most of the articles are about D&D and gaming in general (they are thought provoking).