We’re used to central A/C, so we were surprised by this PIC controller based heater controller. It’s based around a pump controlled boiler/radiator system. A PIC 16F84 is used to input the set point and control a pump to circulate the heated water as needed. You can grab full schematics on the project page.
Update: We added a screen capture of the schematic after the break since the site keeled over.
The image is wider than our normal column width, so right click and view it to see the entire image.