Toonel.net offers a technique to conserve network bandwidth by attempting to compress resources transferred thereby increasing connection throughput. We recommend our solution for those who are paying a fee based on traffic consumption; have monthly download limit or using narrowband connection.
This review was originally posted on VersionTracker.com. Indeed there is no readme, but take a look at the developers' site for detailed instructions on how to set proxies for your browser, mail client, etc. The folks doing this appear to be very Mac friendly so it would be good to give them encouragement. It does seem that they will eventually charge for the service.
Make life easy on yourself: set up a new location in the Network Preference Pane (ie "AirPort--toonel proxy") and then do the FTP, HTTP, and HTTPS proxy tweaking on this location. That way you can easily switch locations -- back to your usual settings -- to test how much (or little) toonel is doing for a particular site.
An added bonus: since I live in China this also happens to be an easy way for me to surf as if I'm in the United States, thereby circumventing Peking's lockdowns on many parts of the net. Most handy indeed-- it certainly beats poking around for the proxy site du jour.
One caveat-- secure toonel connections haven't worked well for me, but that may also be a function of being behind the Great Firewall. . .