D&D May Sale. 20% off over 9,000 D&D PDFs including, I think, everything from WotC. It says some individual items and bundles 66% off for flash sales but I do not see those yet.
Goodman Games 3e Throwback Sale. All 3e PDFs are $1, $3, or $5. This includes Dungeon Crawl Classics, Etherscope, Complete Guides, DragonMech, Judges' Guild, Wicked Fantasy, X-Crawl, and more.