ActiveState is a company which, among other things, distributes pre-built versions of the Python language. Their products are mainly used on Windows environments.
What ActiveState says about itself, taken from their About page:
ActiveState is the leading provider of tools and services for dynamic languages such as Perl, PHP, Python, Tcl and XSLT. The key features of dynamic languages: high-level, dynamically typed and open source, make them ideally suited to building loosely coupled systems that adapt to changing requirements.
These languages solve real programming challenges, proving themselves both in spite of — and thanks to — their independence from corporate platform strategies.
From high-quality language distributions for general purpose scripting; to professional development, debugging and deployment tools; to services that ensure peace-of-mind and stability of essential systems, ActiveState is committed to providing dynamic tools for the dynamic languages powering essential projects everywhere, from the birth of the web to tomorrow's challenges.