http://code.google.com/p/diffable
Diffable works by transmitting deltas between cached versions of a static resource, rather than the entire new version, when the given resource changes.
I've been working on implementing this on Google Maps for a few months now, and today I presented the open source project at the O'Reilly Velocity 2010 conference.
I respect this site and its users immensely and welcome all feedback and participation. Thanks.
clicky