Take a look at BrewPi, a fermentation controller made with a Raspberry Pi. The project hacks control of a refrigerator and a light bulb into the pervue of a Raspberry Pi board. The RPi itself brings network connectivity to the mix. What you end up with is an already highly configurable fermentation system which is perched to receive even more features moving forward.
The man behind the system is [Elco Jacobs]. You may remember his name from the UberFridge project. That was a router-based fermentation controller. This keeps the same great hardware as well as online graphing and control features such as setting plot points for ramping temperature up and down. For now there’s also an Arduino being used which takes care of the hardware switching via json packets received from the RPi. But now that he’s worked out most of the bugs it should be fairly painless to dump the Arduino and build a proper RPi shield for this purpose.