Arduino FIO based weather station with a DHT22 temperature & humidity sensor and a BMP085 barometric preassure sensor. The whole sensor will be powered by a solar panel (doubling as irradiance sensor) and backed by a LiPo cell.
You can read about this project in my blog: Weather Station.
Rocket Scream Lightweight Low Power Arduino Library https://github.com/rocketscream/Low-Power
Ben Adams' Arduino library for the DHT22 humidity and temperature sensor https://github.com/ringerc/Arduino-DHT22
Adafruit BMP085 Library https://github.com/adafruit/Adafruit-BMP085-Library
Tinkerkit secret voltmeter & thermometer for the Arduino 328 https://github.com/timofonic/tinkerit/blob/wiki/SecretThermometer.md https://github.com/timofonic/tinkerit/blob/wiki/SecretVoltmeter.md