ASN.1 library for Python
- A ASN.1 types and codecs implementation. [Open Source, BSD]
- http://pyasn1.sourceforge.net/

LZO
- Python bindings for the LZO real-time data compression library. [Open Source, GPL]
- http://www.oberhumer.com/opensource/lzo/

cx_bsdiff
- A Python extension module for binary patching and diffing. [Open Source, BSD license]
- http://starship.python.net/crew/atuining/cx_bsdiff/index.html

tarfile
- A pure Python module for reading and writing .tar and tar.gz files. [Open Source, BSD-like]
- http://www.gustaebel.de/lars/tarfile/

The ReportLab Toolkit
- A PDF generation library. [Open source, BSD-like]
- http://www.reportlab.org/rl_toolkit.html

ID3.py
- A simple Python module for retrieving and setting ID3 tags on MP3 compressed audio files through an object-oriented interface. [Open Source, GPL]
- http://id3-py.sourceforge.net/

PyLZMA
- Platform independent Python bindings for the LZMA compression library. [Open Source, LGPL]
- http://www.joachim-bauch.de/projects/python/pylzma