The more I look, the more I find.
Post One is here and Post 2 is here.
Goblinoid Games appears to have put it's entire catalogue on sale. That means titles such as Labyrinth Lord, Crypt World, Rot World, Starships & Spacemen, Realms of Crawling Chaos and others.
Kort'thalis Publishing has also put it's entire catalogue on sale. My picks would be Liberation of the Demon Slayer and Revelry in Torth.
Expeditious Retreat Press is another publisher that has put their entire catalogue on sale. Looking for OSR adventures? Look no further. ERP has you covered.
Kobold Press looks to have nearly it's entire line up on sale. Have holes in your Kobold's Guide to... series of releases? Now is the time to fill them.
How about +Kevin Crawford 's Sine Nomine Publishing collection? Yep, 30% off the lot of it. If you can get only one I suggest Red Tide: Campaign Sourcebook and Sandbox Toolkit
Purple Sorcerer Games has put 6 of it's 7 DCC RPG releases on sale. Sunken City Omnibus. Enough said.