Interested in virtualization? Do QCOWs rule your filesystem? Are you a libvirt or KVM+QEMU wizard? I wrote a book about virtual disk management. Check out the The Linux Sysadmin's Guide to Virtual Disks online for free at ScribesGuides.com.
Consider supporting the author by purchasing a hard copy of the first edition for just $10.00 on Lulu.com.
bitmath
bitmath is a Python library for dealing with file size units (GiB's, kB's, etc) in a sane way. bitmath supports arithmetic, rich comparison, conversion, automatic best human-readable representation, and many otherutility functions. Read some examples on the docs site or check out the source on GitHub.