What is mapnik?
Mapnik is a Free Toolkit for developing mapping applications. It's written in C++ and there are Python bindings to facilitate fast-paced agile development. It can comfortably be used for both desktop and web development, which was something I wanted from the beginning.
Mapnik is about making beautiful maps. It uses the AGG library and offers world class anti-aliasing rendering with subpixel accuracy for geographic data. It is written from scratch in modern C++ and doesn't suffer from design decisions made a decade ago. When it comes to handling common software tasks such as memory management, filesystem access, regular expressions, parsing and so on, Mapnik doesn't re-invent the wheel, but utilizes best of breed industry standard libraries from boost.org
What data formats are supported?
At the time of writing mapnik can read all OGR and GDAL supported vector and raster datasets. Mapnik also has a native ESRI Shapefile, PostGIS and TIFF readers, using a plugin framework. More data access plug-ins will be available in the future. If you cannot wait and/or like coding in C++, why not write your own data access plug-in?
Which platforms does it run on?
Mapnik is a cross platform toolkit that runs on Windows, Mac, and Linux (Since release 0.4). Users commonly run Mapnik on Mac 10.4.x - 10.5.x (both intel and PPC), as well as Debian/Ubuntu, OpenSuse, and FreeBSD Linux distributions. If you run Mapnik on another Linux platform please add it to the list on the Trac Wiki
(The homepage is http://mapnik.org and there is a PayPal button on the front page. -Paul)