Palladium has an Alternate Realities Sale 20% off 11 PDFs showing off the Palladium Multiverse including Rifts, Rifts Chaos Earth, the Palladium Fantasy RPG, Recon (the Vietnam war RPG), Nightbane, and Systems Failure.
Remember to hunt around on drivethru and the sister sites for the Halloween icons to get freebie PDFs such as Bygone Bestiary for White Wolf's old World of Darkness.
The Blight is a great corrupt city 925 page sourcebook for $12.19, but check out the massive 952 page Orcus themed wasteland ruined city sandbox Slumbering Tsar Saga for $3.75. If you ever wanted to check out a sandboxy mega-adventure now is a great opportunity.
The Cyclopean Deeps are also great deals for a little more than $3 each for 160 and 250 pages of Descent into the Depths underdark sandboxing.
Over at the non halloween sale for FG's pathfinder line Razor Coast colonialism pirates themed mega-adventure is still a ridiculous steal at $2.50.