Performance and Testing

Psyco
Specializing (like a dynamic) compiler for Python, runs code 2-100 times faster, needs much memory; makes high level language faster. Descriptions, downloads (program, website), documents, news, links. [Open Source, MIT]
http://psyco.sourceforge.net/

PyChecker
A tool for finding common bugs in Python source code. It finds problems that are typically caught by a compiler for less dynamic languages, like C and C++. [Open Source, BSD-like]
http://pychecker.sourceforge.net/

PyLint
An extensible tool that checks if a module satisfies a given coding standard.
http://www.logilab.org/857/

PyUnit
An extensible unit testing framework for Python, based on Java's de facto standard JUnit framework.
http://pyunit.sourceforge.net/

twill
A tool for Web application testing. It implements a simple scripting language that can be used interactively or from scripts; this language contains commands for browsing the Web, filling out forms, and asserting various conditions.
http://twill.idyll.org/