Google announced on Monday a proposal for a new HTTP compression scheme, called Shared Dictionary Compression:
Over the last few weeks we've been experimenting with a way to get better compression for HTTP streams using a dictionary-based compression scheme, where a user agent obtains a site-specific dictionary that then allows pages on the site that have many common elements to be transmitted much more quickly.
Its Google group is here and includes the specification and a very helpful presentation. A quick search reveals that it is based on VCDIFF.
It works like this: the server notifies the client of the potential dictionaries a resource can be based off with a custom header that points to another resource in the server (Get-Dictionary). The client then downloads the dictionaries and on subsequent requests the client tells the server what local dictionaries it has stored locally (kinda like cookies). Then the server sends the resource expressed as a VCDIFF delta over one of the dictionaries the client has downloaded in the past.
Some comparisons could be drawn to fragment-based Ajax, since the VCDIFF delta is effectively the minimal expression of what has "changed" in the page with respect to the dictionary. But since it is implemented as a Content-Encoding at the HTTP level it degrades perfectly on non-Javascript clients and is useful for static content.