Avr_thermo is a project mainly written in C, it's free.
Atmega8/16-based thermostat with simple rtos inside
This project (avr_thermo) is a simple atmega8/16-based thermostat.
I've wrote this project when thermostat in my refrigerator had unexpectedy broken.
I use DS18B20 digital sensor to measure temperature and relay to control the compessor.
This project is based on avr_rtos - mini rtos (with timers, queue and interrupt-driven usart with read/write-buffers).