X-link to the DRM-free thread for the new Humble Bundle:
Humble Book Bundle Astronomy features educational and informative titles about space-based science, from academic/textbook publisher Springer. This is a mix of DIY stuff and accessibly-written layperson-friendly accounts, as well as more advanced materials for the knowledgeable science reading aficionado.
Also, the
Humble Book Bundle Code Your Own Games has added a couple of new software business/management-related titles to the middle tier.