Tim Berners-Lee gave a great talk at TED2009 conference (I have mentioned TED some time ago :-)). He mentions DBpedia which aggregates data from all kind of source...Very interesting! Besides tht also Openstreetmap ist mentioned another great tool.
A video of his talk can be found here.
So do not forget: Tim Berners-Lee needs your raw data!
The slides Tim presented can be found here (Click the screen to get to the next slide)...
