batch http requests

There's an official HTTP way to do that which is called HTTP Pipelining. But you may have more problems with the browser side than with the server-side. So you may be able to use it if you have a hig-level of control on the client side only.

XHR does not always allow pipeling, and AFAIK you have no control of the HTTP tunneling with Javascript. So a basic ajax-jQuery implementation cannot exists. But you may find some advanced things with Comet and the Bayeux protocol, emulating bi-directionnal long-term tcp-connections, where you will certainly reduce the tcp round trips.

I'm not a comet specialist, but you may find useful informations on this Comet & HTTP Pipeling article, to my understanding most of this is highly experimental, but at least you could have a nice fallback with 'classical' comet when HTTP Pipelining is not available. This would maybe need a retag or a new question.

Define a new resource that contains the data the client wants. See http://roy.gbiv.com/untangled/2008/rest-apis-must-be-hypertext-driven#comment-743