Currently I’m working on two Arduino projects, both will upgrade my weather station.
OLED I2C display
The OLED is connected to an Arduino Nano via I2C and it measures the current voltage of the solar powered batteries.
The OLED display is available at wide.hk for 16$.
The other project is pretty cool. I will build a new Arduino Shield for a lightning sensor (AS3935), just announced this week, from austriamicrosystems. Link to sensor page.
This sensor is accessible via I2C respectively SPI. It detects both cloud-to-ground and intra-cloud (cloud-to-cloud) flashes within a 40km range. The supply voltage range is from 2.4 to 5.5V.