Astonishing Swordsmen & Sorcerers of Hyperborea: A 1st Edition AD&D retroclone taking place in a setting heavily inspired by Robert E Howardesque stories.
Red Tide Campaign Setting & Sandbox Toolkit: A Kevin Crawford work, Red Tide is a setting inspired by Asian lands with a touch of other civilizations. A creeping red mist taking over the land forced the last remnants of civilization to the Sunset Isles, inhabited by the vicious Shou.
Sunken City Omnibus: A series of Dungeon Crawl Classics adventures compiled in one book by Purple Sorcerer Games.
Midgard Campaign Setting: A rather nifty setting based on European folklore with some more mythical elements thrown in for good measure. Several other Midgard sourcebooks are on sale as well.
Ponyfinder: A popular book which brought many Bronies into the fandom, Ponyfinder makes some clear homages to the Friendship is Magic franchise. Several other Ponyfinder products are on sale as well.
Southlands Campaign Setting: With one of the writers of Al-Qadim as a contributor, Southlands is a setting is a blend of Ancient Egypt and Medieval Africa and Arabia.
Tales of the Old Margreve: A Midgard series of adventures for PCs levels 1 through 10. They're all set in a primeval forest which seems to have a mind of its own. Features focuses on fey and dark fairy tale-esque themes.
Ultimate Psionics: The definitive Pathfinder upgrade to the 3rd Edition rules, Dreamscarred Press compiles both updated and new material into one megabook.
Numenera & the Strange: Numenera's core rulebook and many other Cypher System products are on sale.
The One Ring: Three setting sourcebooks are on sale. Many fans say that the RPG feels the closest to Tolkien's work in terms of conventions and themes in comparison to the ones that came before.
Parsantium: City at the Crossroads: A system-neutral sourcebook detailing a fantasy counterpart Constantinople. This book provided some major inspiration for my Arcana High campaign, and kickstarted my interest in the Byzantine Empire.
Ptolus: Monte Cook's City by the Spire: A city-focused setting which has a huge influx of adventurers, Ptolus is Monte Cook's magnum opus and rare for the fact that the setting and system integrate together. It fits 3.5 like a glove, and there's little in the way of messy attempts to cram a square peg in a round hole. Ptolus also features the eponymous Spire and many underground dungeons which see so many delvers entering the city.