if you happen to understand German, I'd like to point you to a recently published podcast episode which features the Overpass API and its developer, Roland Olbricht. "The Overpass API (or OSM3S) is a read-only API that serves up custom selected parts of the OSM map data. It acts as a database over the web: the client sends a query to the API and gets back the data set that corresponds to the query." (*)
In this extensive interview, Roland talks about the Overpass query language and its underlying design principles, about the OSM developer community, and about future challenges and ideas (64 bit node IDs, federated databases, permanent IDs, dynamical cleaning of tagging information - to name just a few).
Link to website (including show notes and comments): http://blog.openstreetmap.de/2012/12/osmde009-osm-talk-die-overpass-api
Direct link to audio file: http://audio.podcast.openstreetmap.de/OSMDE009.mp3
This is a special installment of the German OSM podcast "Radio OSM". For a list of all published episodes visit: http://blog.openstreetmap.de/radio-osm/