The TMP36 was my first sensor and is pretty simple. 3 pins, 1 analog port.
Available from SparkFun.
It’s a low voltage temperature sensor. It provides a voltage output that is linearly proportional to the Celsius temperature. It also doesn’t require any external calibration to provide a typical accuracy of ±1°C at +25°C and ±2°C over the −40°C to +125°C temperature range. Give the it a ground and 2.7 to 5.5 VDC and read the voltage on the Vout pin. The output voltage can be converted to temperature easily using the scale factor of 10 mV/°C. For Example: