In the past, Python module developers have not had much infrastructure support for distributing modules, nor have Python users had much support for installing and maintaining third-party modules. With the introduction of the Python Distribution Utilities (Distutils for short) in Python 1.6, this situation should start to improve.
This document only covers using the Distutils to distribute your Python modules. Using the Distutils does not tie you to Python 1.6, though: the Distutils work just fine with Python 1.5.2, and it is reasonable (and expected to become commonplace) to expect users of Python 1.5.2 to download and install the Distutils separately before they can install your modules. Python 1.6 (or later) users, of course, won't have to add anything to their Python installation in order to use the Distutils to install third-party modules.
This document concentrates on the role of developer/distributor: if you're looking for information on installing Python modules, you should refer to the Installing Python Modules manual.