polipoly is a project of Sunlight Labs developed for the purpose of dealing with political boundaries.
At the moment the library focuses on the boundaries described by CensusShapefiles but other uses that match the target purpose are possible.
Dependencies
Installation
At the moment polipoly consists of a single file: polipoly.py
The latest version can be obtained from public SVN http://polipoly.googlecode.com/svn/trunk/polipoly.py
polypoly also exists in PyPI so it can be installed via easy_install polipoly on supported systems.