For one, I managed to score a number of freebies over on RPGNow.com and WargameVault.com as part of their Halloween jack-o-lantern hunt (think Easter eggs, but with jack-o-lanterns).
Throughout their sites, DriveThruRpg people have hidden jack-o-lantern icons that link either to a trick or a treat. All of the "treats" are horror-themed pdf downloads you'd normally have to pay for, while the "tricks" vary from weird videos on youtube to funny "very demotivational"-type images. Each site is different, so stop by them both!
|My cat, Pumpkin. She is not a jack-o-lantern. Nor does she have any downloads for you.|
Just on title alone, two that stand out are Fear and Faith by Ganesha Games and Werewolf: The Apocalypse Rev. Ed. These are quality products by respected gaming companies (and ones I've considered purchasing at various times). Right there, that's over $26 in free stuff. Even better, it's stuff I'll probably use.
Unfortunately, I can't remember where the links for those were hidden exactly. Just focus on the pages anyone visiting the site might look at - main page, new products, your account pages, etc - and you'll find most of everything.
Good luck and happy hunting!