Thanks to its open data and its renderers, OSM has great customizing potential for its maps, well beyond simple color tweaking and such. While this is obvious for XML-aware people, this is not (and can't be) obvious for noops. I would like to develop an usable WYSIWYG GUI frontend for Osmarender that will be available as a web application and as a downloadable standalone application. Furthermore, its core (which will handle Osmarender's rules/styles editing features) will provide a well-documented and well-tested public JavaScript API to let other contributors develop other applications. This will benefit OSM project as a whole, because

1) For users: Thanks to the usable WYSIWYG GUI, it will let common people start to really interact with OSM data. A wiki-style gallery for custom rules and styles will also provide that Web 2.0 taste to attract more non-tech people, so enhancing OSM spreading. Furthermore, its hybrid web/standalone architecture will let common people download the standalone version for time-consuming renderings, or to customize their rules/styles without an Internet connection, thus letting non-broadband/non-flat-connected users contribute anyway.

2) For developers: The public API will let other (even beyond OSM's) developers start new Osmarender handling projects, on a solid base and in a simple way. This will lead to an unpredictable number of new applications and contributions.

Thanks to Osmarender's XSLT-approach and my application's hybrid JS/PHP architecture, all this features will be achieved without loading OSM's server, thus scaling well.