Packt Publishing offers a
free book every day, although the selection is random. These are all computer/networking stuff. I've been grabbing them nearly every day since August or so and have built up quite a collection. Most books are available in DRM-free Epub, Mobi and PDF formats. Some are only available in PDF, but in my experience those are pretty rare. (Three out of 176 total eBooks.)
If you do take advantage of it, be sure to check the E-mails Packt Publishing sends out. They sent me a coupon for a free eBook of my choice once, no strings attached.
