DS18B20 Digital Temperature Sensor is a fairly precise 1-Wire temperature sensor which can give up to 12 bits of precision from the onboard digital-to-analog converter. These sensors work great with any microcontroller using a single digital pin, and you can even connect multiple ones to the same pin, each one has a unique 64-bit ID burned in at the factory to differentiate them. You can use the sensors with both 3.3V and 5V systems.
The only downside of DS18B20 Digital Temperature Sensor is it uses the Dallas 1-Wire protocol, which is somewhat complex, and requires a bunch of code to parse out the communication. There's a great Arduino library for 1-Wire, but some microcontrollers do not have support for 1-Wire.
There is a 4.7k resistor, which is required as a pullup from the DATA to VCC line when using the sensor. A detailed tutorial is not up yet, but you can get started by using the Dallas Temperature Control Arduino library which requires also the OneWire Library.
Dallas Temperature Control Arduino Library: http://www.milesburton.com/?title=Dallas_Temperature_Control_Library
OneWire Library: http://www.pjrc.com/teensy/td_libs_OneWire.html
Adafruit Web Site: https://www.adafruit.com/product/374