A little web service that allows you to subscribe to PubSubHubbub feeds from Javascript!
GET http://pubsubjubhub.appspot.com/?
hub.topic=http://superfeedr.typepad.com/blog/atom.xml&
hub.callback=http://myapp.com/push/123&
hub.mode=subscribe
Of course, you can also specify a hub.verify, a hub.lease_seconds, a hub.secret, a hub.verify_token, and you can force the url hub, by providing hub.url...
And for all these feeds which do not have a designated hub, you can as well specify your superfeedr.login and superfeedr.password if you have a Superfeedr account. It will also echo any HTTP header that you use in your request.
Finally, You can as well add a callback parameter.
{"code":"200", "All Good!"}