For the computer programmers in the audience, Packt Publishing will be offering a free ebook every day through May 17th (DRM-free ePub/Mobi/PDF bundle with an online read option).
Here's the promo page which will showcase them all (they're operating on GMT and rotate daily ~ 4 PM Pacific Time), and you'll need to already have an account with them to claim each title to add to your library:
Free Learning — Help Yourself, and today's freebie is for
Kinect in Motion – Audio and Visual Tracking by Example
This week's
Humble Weekly Bundle: Indie Game Magazine will give you two free issues of the titular magazine (April 2014 & 2015, DRM-free PDF) just for putting your email address into the box (no need to actually sign up for the newsletters if you don't want to). And should you also be interested in the games, three of the weekly bundle titles are DRM-free (and 2 of those available for Linux as well as Mac and Windows).
Also, Wildside hasn't yet pulled their weekly Tuesday freebie, so for now you can still get the
Richard Deming Crime Minipack directly from their promo page if you missed it earlier.