ActivePython from ActiveState is a commercial-grade, quality-assured Python distribution focusing on easy installation and cross-platform compatibility on Windows, Linux, Mac OS X, Solaris, HP-UX and AIX. It includes numerous useful modules in addition to the standard libraries and allows for quick installation of additional modules via PyPM (Python Package Manager).
PyPM Index shows which modules are available on various platforms, and allows you to search by package name, author, tag, or what the module imports.
Several versions of ActivePython are available:
Community Edition: Free distribution, ideal for community developers with open source projects.
ActivePython Business Edition: For SMB and government with business critical applications. Per-server licensing and support.
ActivePython Enterprise Edition: For large enterprises with mission critical applications. Customizable support program and optional legal indemnification.
ActivePython OEM: Redistribution rights for ActivePython with optional support and legal indemnification.
ActiveState is one of the most well known and one of the longest running suppliers of Python distributions, tools, and support.