Google has a whitepaper on an application-layer protocol for transporting content over the web, SPDY, pronounced "speedy." In tests, it shows some huge improvements over regular HTTP as we know it.
SPDY is designed to allow multiplexed streams (to allow unlimited concurrent streams over a single tcp connection, also present in WebSockets), request prioritization, and http header compression. The advanced feature set allows server-initiated streams, which allow explicit server push (which sends data before a client requests it) and server hints (which suggest that the client should download resources before the client determines the resources are needed).
Right now, you need a custom server and a custom browser to try SPDY; the server is not open source yet, but should be soon. Preliminary results look very nice: the worst speedup was on DSL (which nobody uses any more, but testing is nice) with a speedup of 28%. (Judging solely by packet loss, speedups were a lot less drastic, but that sort of make sense: most speed promblems look like they're based on streaming issues and not packets disappearing.)
The neat thing about SPDY is that it looks like it can piggyback on the regular HTTP stream - which means we could see SPDY as an option for high-performance servers in Java.