X-link to the DRM-free thread for some new bundles:
StoryBundle's
The A. I . Bundle is curated by author Lisa Mason, and contains backlist novels by Mason, Linda Nagata, Walter Jon Williams, as well as few newer works by additional contributors and two anthologies.
The Humble Book Bundle The Horus Heresy presented by Black Library contains mostly tie-in novels for the popular Warhammer sci-fantasy RPG setting, plus a few audio dramas, and some other things.