OpenGeoData used to be the main OpenStreetMap blog at opengeodata.org . It was unified into blog.openstreetmap.org . See Main blog.openstreetmap.org blog.
History of the blog
The OpenGeoData.org blog started out as a blog by Steve Coast about the OpenStreetMap project. It also featured various guest postings. It was always regarded at the "main" blog of the OpenStreetMap project, and was linked from the OpenStreetMap.org front page.
At some point the domain name opengeodata.org was pointed to the posterous blogging service where Steve carried on blogging. An archive of old posts remained in a wordpress site at old.opengeodata.org
Gradually the blog transitioned to have many other contributors, lots of news with quite and official tone, and fewer personal opinions of Steve. The Communication Working Group did most news postings there in 2012, as well as posting to blog.osmfoundation.org with more official foundation news. In May 2013 it was decided that this distinction was more confusing than useful. Posterous was also closing down. A tidy newly skinned newly unified Main blog.openstreetmap.org blog was set-up.
All posts were merged with those of the osmfoundation.org blog. Old posts at old.opengeodata.org were also merged in at this time.
The opengeodata.org site now carries redirects, but these may go away or be repurposed at some point.