Here is a temperature sensor that is able to measure a wide range of temperatures while being energy efficient. Its analog output is proportional to the ambient temperature.
This sensor is very popular and really easy to implement. This is one of the elements of the ARDX kit.
To use it, simply connect pin 1 (left) to a power source (between 2.7 and 5.5V), pin 3 (right) to ground (GND) and finally pin 2 (middle) on an analog input of your micro controller.
The output voltage is 0V at -50°C and 1.75V at 125°C. It is easy to convert the output voltage (in millivolts) to temperature using the formula:
Temp °C = 100*(V reading) - 50
The data sheet of the TMP36 is available here.