The Yahoo! GeoPlanet data is available for download but this data only includes the object hierarchies without any associated geometry.
Do anyone know if there is an open source for geometry (centroids or otherwise) for associated WOEIDs? I wonder if there's a lesser-known link somewhere on the GeoPlanet site, or perhaps another party has done some work to correlate open data sets (census, geonames, etc) with WOEIDs.
A WOEID (Where on Earth IDentifier) is a unique reference identifier assigned by Yahoo! to identify any feature on Earth.