Application Server: Zope
by The EditorZope is a cross platform application server for building online systems and is available for Mac OS X, Windows and Linux. Mac OS X does require some special compilation.
From the Zope website:
Zope is an open source application server for building content management systems, intranets, portals, and custom applications. The Zope community consists of hundreds of companies and thousands of developers all over the world, working on building the platform and Zope applications. Zope is written in Python, a highly-productive, object-oriented scripting language.

