Update (2007-06-22): No DELETE, but you can POST an Atom entry to /features.atom and PUT to any of the individual entry edit URLs. I also verified the service document and collections using Joe Gregorio's APP Test Client.
I haven't added PUT or DELETE yet, but Hammock is close to satisfying the read-only aspects of the Atom Publishing Protocol. The service document links to the single collection represented as a feed. Every resource now has alternate XHTML representations, which are created using Genshi: service, collection, and item.