My site, for example, is at http://jmathai.openphoto.me/photos/list. You can add ".json" to the end to see the JSON representation of that page. http://jmathai.openphoto.me/photos/list.json. The same rule applies across the site.
We wrote about it a while back.
http://blog.theopenphotoproject.org/post/8462620991/clean-ur...