This is a weather/home automation oriented project based on Arduinos.
It consists of main unit (Arduino Mega 2560) and remote unit (Arduino Pro Mini).
Remote unit is just battery/solar powered box with some sensors and radio module which sends sensor readings to main unit.
Main unit consists of some sensors as well as some relays.
Monitor variety of environmental variables such as temperature, humidity, rainfall, ligh etc.
You can get actual sensor readings and relay states from main unit's LCD or web interface.
Graph sensor readings using ThingSpeak, and evaluate how is your environment changing over time.
Control main unit's relays directly from web interface, or schedule automatic rules based on sensor readings. You can also measure and graph power consumption of attached appliances.