This is a small project I've been working on to control a heater (or really anything) via a Raspberry PI, a powerswitch tail, and 0 or more sensors. Currently I'm planning on using this for regulating the heating cable for my beer fermenter, and hopefully for a small heater for a wood drying kiln.
DHT code adapted from the following tutorial. http://learn.adafruit.com/dht-humidity-sensing-on-raspberry-pi-with-gdocs-logging/software-install