codeathon of Wikimania 2009 was the OpenStreetMap (OSM) integration into the Wikimedia Foundation projects. When Wikipedia is to use OSM, there will be a big demand for its data so much of the work is about infrastructure and scalability.
As many of the people involved come to a Wikimania, it was great to learn how Slippymap and Semantic Maps relate. It turns out that the bulk of the work done is applicable to either extension and, that Semantic Maps brings together other map functionality.
The joy of having people together is that Aevar discussed with Siebrand the possibilities of localising OpenStreetMap at translatewiki.net. One of the arguments in favour is that OpenLayers is already localised at translatewiki. This is now being discussed by the OSM developers, there are issues that will need to be resolved, but the arguments are sound.
With Wikimedia projects using the OpenStreetMap data, it is obvious to me that our localiser community will be happy to make OpenStreetMap even more awesome.