DS18B20 digital sensor. It uses one pin to communicate with the Arduino, along with +5vdc and Gnd. We add a 4.7k resistor between pins 2 & 3. Because we are using a single sensor, we do not need to know the address of the DS18B20 ahead of time. If you want to add a second sensor, to display outdoor temperature see our other tutorial. We are using the DS18B20 code from http://arduinotronics.blogspot.com/2010/11/ds18b20-digital-thermometer.html and the LCD code from http://arduinotronics.blogspot.com/2012/06/lcd-keypad-shield.html
Don't forget the updated One Wire and Dallas Libraries from http://www.hacktronics.com/Tutorials/arduino-1-wire-tutorial.html
Pin 1 on the left is Gnd, Pin 2 in the middle is +5vdc, and pin 3 on the right is data, according to the GVS standard we follow.