DHT22 Temperature and Humidity

From Adafruit.com

The DHT22 is a very common temperature and humidity sensor. It is the more accurate version the DHT11.

TECHNICAL DETAILS

• Low cost
• 3 to 5V power and I/O
• 2.5mA max current use during conversion (while requesting data)
• Good for 0-100% humidity readings with 2-5% accuracy
• Good for -40 to 80°C temperature readings ±0.5°C accuracy
• No more than 0.5 Hz sampling rate (once every 2 seconds)
• Body size 27mm x 59mm x 13.5mm (1.05" x 2.32" x 0.53")
• 4 pins, 0.1" spacing
• Weight (just the DHT22): 2.4g

Datasheet

Wiring with Raspberry Pi

Also sold as a wired version (rather than a breadboard version).