Mapnik is a Free Toolkit for developing mapping applications. It is written in modern C++ and has Python bindings that support fast-paced agile development. It can comfortably be used for both desktop map design and web development.
Mapnik is about making beautiful maps. It uses the AGG graphics library, which offers world-class anti-aliasing rendering with subpixel accuracy for geographic data.
See the the Mapnik FAQ for more information.