Joe Gregorio's atompubbase looks promising. To try it out, I ran the apexer program against my Hammock site:

sean@lenny:~$ apexer service
sean@lenny:~$ apexer lc
0   Places
sean@lenny:~$ apexer collection 0
sean@lenny:~$ apexer ls
0   Theater at Hierapolis
1   Springfield/Ninoe
2   Springs at Hierapolis
3   Big Hendy Grove
4   Little Hendy Grove
5   Navarro Vineyards
6   Wehlener Sonnenuhr
7   Pic St-Loup
8   Vineyards Domaine de l'Hortus
9   Vineyards Domaine de l'Hortus
sean@lenny:~$ apexer entry 8
sean@lenny:~$ apexer get
sean@lenny:~$ cat entry
<?xml version="1.0" encoding="utf-8"?>
<entry xmlns=""
  <title>Vineyards Domaine de l'Hortus</title>
  <link rel="alternate" type="text/html"
  <link rel="edit" type="application/atom+xml"
  <link rel="edit-media" type="application/"
    Mourvedre, according to
    <gml:Point xmlns:gml="">
      <gml:pos>43.7896297407 3.83361116447</gml:pos>

I edited that entry and posted it back to the collection:

sean@lenny:~$ apexer create entry --content-type="application/atom+xml"
sean@lenny:~$ apexer ls --all
0   Theater at Hierapolis
1   Springfield/Ninoe
60   Duplicate Vineyards Domaine de l'Hortus

See the result. Publishing geodata can be as simple as that. I don't think AtomPub is going to take over the geospatial world in 2008 -- few of our architects have even heard of it yet let alone begun to dabble outside WxS -- but we'll see a few more high profile implementations. Google Earth as an AtomPub client maybe? The services (Picasa, YouTube, etc) are certainly there already.