* per-user ICBM coordinates (history). go to http://www.livejournal.com/admin/console/ and "set icbm 37.7788,-122.3974", then it'll show up in your HTML meta tags on your (main) journal page.
* per-entry ICBM ("prop_current_coords"). no way to set this on the web, and probably won't be. it exists in the protocol already, though. it must be of a standard format. you can use the format above safely. read LJ::Location if you want more details.
* per-entry "Current Location". this is on the web already, but it's not totally sexified up yet. this is free-form text. you can type "Flagstaff, AZ" or "home" or "outside" or "on the train" or whatever. later, if we can geocode it, we'll set the per-entry coordinates for you. or (later) if you upload a photo with geo EXIF in it, we'll set the corresponding's entry coordinates to that of the picture.
More later, I'm sure.