The Hollow Ground: A Novel by Natalie S. Harnett: Okay, this is not gaming stuff but it is the debut novel written by +Erik Tenkar's (Tenkar's Tavern) sister. I figure that it makes it gamer-related (maybe? sort of?). My wife, Deb (World So Sweet), just finished reading it and gave it two thumbs up. Once she started, she didn't put it down. It sounds like she will be recommending it to her book club the next time they meet. It is on my "To Read" shelf for this weekend, right behind the latest Jim Butcher Dresden novel, Skin Game.
A Magical Medley (Fudge): A collection of magical systems for Fudge-based games, although it would fairly simple to convert to GURPS or Fate. African, Celtic, Chinese and Occult magic are all included, plus Bioenergetics (which seems like a bit of an outlier here).
A Magical Society: Silk Road: A supplement with lots of info and tables for using the Silk Road as an RPG setting (or at least borrowing from it). The print version is out-of-print, but I was able to order it used from Amazon for less than $15 (including shipping). The PDF version is still available for purchase/download. I have toyed with a Silk Road based setting that could be used with GURPS, Savage Worlds, or a D20 rule set.
Red Tide: Campaign Sourcebook and Sandbox Toolkit: I decided to get this in print and PDF. It is quite good and it has a lot things that could be lifted to incorporate into another setting.