General

• http://en.wikipedia.org/wiki/Geocoding
  
  Overview of encoding and use geographic information.
  

• http://en.wikipedia.org/wiki/Geotagging
  
  Overview of a number of existing geotagging scheme and informal standards (flickr, wikipedia, flickrfly w/ google earth, etc)
  

Atom
GeoRSS and GeoAtom seem to be synonymous.  Haven't found docs on standard.

http://www.geobliki.com/articles/2007/08/06/a-wfs-basic-as-a-geo-atom-store

Atom Resources

GeoPress

GeoPress is a WordPress/MT plugin that adds geocoding & mapping to blog posts.  They also add geo data to feeds.