Not OSR, but I am partial to the old gamebooks (A couple months ago when my internet was down, I played a bunch of the old Fighting Fantasy ones), so check out The Dungeon of Abkadev, a PWYW gamebook.
FRC1 Ruins of Adventure - This is one of my favorites. It's an adaption of the first SSI Gold Box computer game, Pool of Radiance. Although it follows the same basic premise and uses the same maps, much of the details are different and changed for better play at the table. It's really basically a sandbox - the PCs are left to their own devices to explore and help restore a ruined city. 96 pages, $4.99
WG8 The Fate of Istus - This large Greyhawk adventure was meant to change your campaign from 1st edition to 2nd edition. I didn't think much of it at the time, but it has a few nice bits, like describing some of the cities. $4.99, 128 pages.
WG10 Child's Play - This is a 2e introductory adventure (though somehow meant for high level characters) that showed that post Gygax TSR had no idea what to do with Greyhawk, as this is Greyhawk in product name, but not actually in Greyhawk. 32 pages, $4.99
The Curse of Harken Hall - A first level OSRIC adventure, the players are hired to investigate a secret door in a manor. $5.45 (I'm guessing this makes more sense in a different currency, probably pounds given the author is named Simon which is perhaps the most common English name besides Ian and possibly Nigel) and 35 pages
Necromancer's Bane - The sequel to the above (which is why I didn't put it first) meant for 2nd to 5th level characters and more of a dungeon crawl. 57 pages, $5.45.
The Tales of Highguard Cliff - More an adventure setting than adventure, but meant to provide background for The Curse of Harken Hall. 73 pages, $5.45
Back to the Dungeon Book 1 Races and Classes - I'm not sure this is really OSR in my point of view (as it's not particularly close to TSR era D&D), but the guy has been working on it for years over at Dragonsfoot. $2, 44 pages
Back to the Dungeon Book 2 Monsters and Traps - See above. 44 pages, $4
Back to the Dungeon Book 3 Games Master's Guide to the Ancient World - This seems to be more about GMing than a description of a world. 44 pages, $4.
MiscEnhanced Friday Freebie - Improved version of one of Paratime Design's free maps. $1
Lamentations of the Fire Princess Everything Bundle - For $168, you get pretty much everything. Personally, I'd rather have the money. I bought most of it back during their $1 a product sale. Most of the stuff just isn't very good, more pretentious than anything else. Maybe if you like masochist players who like getting railroaded. A few exceptions though, like World of the Lost (though even that traps the PCs)
Hobgoblin Lair - Nice 2 pages map of a hobgoblin lair. $3
OSR NPC Generator Cards - Because dice are apparently just so hard. $5, 22 pages
White Box Character Sheet - Free character sheet for S&W White Box. But wait, doesn't the very concept of character sheets go against the White Box school philosophy?
White Box Referee Screen - See above. PWYW.