The New York Times has an article today on geotagging. Unfortunately, support for geotagging is different across the various photo sharing services. Where you really want to do this is at the camera, when the photo is taken. Today, you have to do that with a GPS external to your camera, and then find a way to get the location data into the EXIF data in the photo. I wonder when Canon or Nikon will include GPS functionality in a prosumer SLR.