As a programming language, Python is the foundation of many software projects producing things like applications, libraries, modules and packages. Since so many projects exist, it can be difficult to find one which is concentrating on a particular topic of interest, but there are several starting points:
Applications - a list of Python-based applications
UsefulModules - libraries, modules and packages
PublishingPythonModules - places where modules are often publicised
SourceForge hosts open source Python-based software projects:
Browse for projects written on Python
Python Source is a directory of open source python projects.
Packageupdates.org lists "top" and "hot" Python packages. The site can also send email notifications for package updates.
PyDoc.net provides package and source code navigation with advanced search features.
Useful code does not always exist in the context of a project - smaller fragments may be published in various places:
Code - a list of small code fragments
The Python Cookbook - a site with pieces of code, rated and commented
Ideas for New Projects
Sometimes there is no project addressing a certain need, or perhaps a project has been started and requires help to reach its objectives.
CodingProjectIdeas - a list of ideas for projects of various sizes
Statistics on Projects
For those who like statistics, some resources exist cataloguing the size and popularity of some Python projects: