Thermostats are handy devices around the house. They can be used in various places like for keeping constant room temperature. Phil suggests one that was specially designed to keep storage room temperature around 6 degrees of Celsius above zero.
This is an AVR Attiny2313 project that interfaces 1-wire temperature sensor DS18B20. Controller is controlled by two buttons while seeing information on three 7-segment LED display. Temperature heater is switched by using relay. Thermostat is designed to be a stand alone device that takes power from mains. So there is a power transformer used and linear regulators to get needed voltages. Overall this is really simple but handy project.