The good old Tenkar of the Tenkar's Tavern signals us a double bundle over the RPGNOW site
an OSR Extravaganza: http://www.tenkarstavern.com/2017/05/rpgnow-osr-extravaganza-sale-15-off.html
where you can find the pdfs of D&D Rules Cyclopedia and the Gazetteer of the Know World from gaz1 to gaz14 for 15$
and you can find also the pdfs of 8 core books of AD&D 1st edition for 15$ (Player's Handbook, Dungeon Master Guide, Monster Manual I, Monster Manual II, Fiend Folio, Oriental Adventure, Wilderness Survival Guide and Dungeoneers Survival Guide) yes I know the Deitas & Demigods is missing as the world book... but still it's a steal: http://www.tenkarstavern.com/2017/05/ad-1e-core-books-mega-bundle-on-sale-at.html
before buying go to the Tenkar's Tavern so you will help the Tavern!