For the last few months, I have been involved in the open source mapping project Openstreetmap. It can be described as an open-source Google maps alternative: They collect the world, and have their database open for anybody to use and edit. So instead of just being able to view the maps, you are also able to get the underlying data. The database consists of basic nodes and vectors, that describe the whole world. These descriptions can be rendered into graphics, by several renderers. One of the main renderers (and the one used on the standard map on openstreetmap.org) is Mapnik. It loads the data from the database, and can output graphical maps, with styles described in stylesheets.
Until now, modifying those stylesheets was often a tedious task of edditing files, and pointing a renderer at them, often at some server (as not many users have the nescascarry software installed to render these maps).
To ease this process I build an online render tool: You can edit the style file, choose a bounding box, and immediately see the results online. A screenshot is shown above: The editor can be found at http://tile.openstreetmap.nl/~panman/styledit/
If you build a nice style, let me know!
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