This is an interesting javascript library that will actually parse each chunk of a multipart/mixed mime response as it comes in. I’m not sure if it has HTTP Pipelining’s same weakness of returning the results in the same order as requests, but you could easily modify the ordering that the library accepts, since you don’t have to worry about http firewalls or load balancers trying to collate the requests and responses for you, because everything is in a single request and response. Of course, this means that multiple requests will hit a single app server, so you would have to roll your own load balancer if that’s something you need.

http://about.digg.com/blog/duistream-and-mxhr