Not a lot of stuff that is directly OSR (in my view, mimicking the TSR era D&D games), but a lot of pseudo-OSR stuff, such as 30% off of Dungeon Crawl Classics PDFs and pretty big discounts on Castles & Crusades PDFs.
If you have any interest in self-publishing, Raging Swan is having a 40% off sale. They produce a lot of reasonably priced and very neat town maps that have a nice hand drawn look (since I guess they are hand drawn). I picked up a couple this summer for a module I'm working on (almost done).
And again, for self-publishing, Purple Duck has 40% off their stock art (which is already really cheap at $3 each when not on sale) and so does Rogue Genius (even cheaper at $1.99 when not on sale, and only $1.11 now).
Purple Duck also has a small line of Labyrinth Lord adventures on sale.
North Wind is selling the Astonishing Swordsmen & Sorcerers of Hyperborea boxed set for $40, vs the usual $50.
Noble Knight is having a small sale. They are an out of print reseller. I remember him from the days when he just sold on Usenet.