Humidity and Temperature DHT11 Module

This is a very popular, ultra low cost digital temperature and humidity sensor. It uses a capacitive humidity sensor, and a thermistor to measure the surrounding air temperature. The result is available via a digital signal on the data pin (no analog input pins needed). Its fairly simple to use, but requires careful timing to grab data. The only real downside of this sensor is you can only get new data from it once every 2 seconds. But, for most applications this is not an issue at all.