If you are throwing together an arduino board to be a thermostat, consider using a Dallas/maxim sensor. They are pretty darn accurate and don't drift or bounce around like a thermocouple or thermistor. If there is only one sensor per wire, the code is real easy.
The little brick I did up for the general purpose controller discussion works with an uno board and an eBay LCD keypad shield. I have the code posted on github, see the thread:
http://ecorenovator.org/forum/geothe...ontroller.html
As AC suspected at the beginning of the project, a single design was never fully developed. The list of functions varied from member to member, as did communication and sensing protocols. Many members upgraded to the Mega board to avoid running out of pins or comm ports. Even so, if you parse through the thread, there were a number of functional units built, with code that was tailored to meet specific design needs or functionality. You can pick, mix and match code from the builds to make your stamp do what you want.
I am in the process of throwing together another dirt cheap window heat pump as time allows for a buddy. I will be using the uno stamp I built last time to control it, and I may end up expanding the functionality of it to avoid having to install a defrost control board in the new (old) unit. Time is tight at present, so I have not been devoting much of it to the build. When I get the unit together, I will start another thread on it.