I just picked up a Honeywell RTH221 programmable thermostat from Home Depot. The cost was under $25. I found it to be very well designed with a simple user interface and well thought out features. Check out the specs here:
http://yourhome.honeywell.com/Consumer/Cultures/en-US/Products/Thermostats/Do-It-Yourself/Programmable/1-Week/Default.htmIt is intended for 24 volt home HVAC systems and has lots of printed circuit Varistors to limit its application to that voltage but it will interface directly to an X10 Powerflash module out of the box.
If you want to push the envelope and use it more generally the relay is rated for 0.5 amps at line voltage. To use it that way, which I did, you can easily remove the tiny varistors from the PC board in less than a minute without a soldering iron. Of course this voids the warranty. Just be careful of the two wires that run from the PC board to the Thermistor that is potted into the cover as a temperature sensor.
