If you love gardening you might find this project useful. This smart garden pot lets you keep track of soil moisture and automatically waters your plants for you. An Arduino is used to interface between a humidity sensor and a relay which turns on a pump which provides water to your plants! Hendra Kusumah who has put this project together has included full code examples and schematics so it should be easy for you to get started. If you want to get started with this project check out the following link.
Looking for a temperature sensor to use in this project? Why not check out the Freetronics Humidity and Temperature Sensor Module?
The module only requires three wires: GND, power and data. This means that it is very easy to get started recording temperature and humidity data! The find out more visit the product page.