As Kobuki and others have pointed out, there is a lot of data out there regarding the various hardware hacks and reverse engineering efforts on the Davis weather stations. It is difficult for new people coming on board to do all of the research to learn about the subject and get involved.
So today I've done something that I've been meaning to do for a long time: I've started a wiki on Github that is a start at tying a lot of stuff together. The majority of the content is on the message protocol, but I've also got pages that start to list some of the cool hacks out there, along with some information on the RF side of the protocol. There is still lots to do, some stuff is probably incorrect, and I may have either totally forgotten something, linked to the wrong spot, or whatever (ever see the very first Wikipedia entries???). None of that is intentional. I've put this together pretty quickly and would welcome anyone interested to make additions and corrections.
Check it out here, and please contribute!
