DS18B20

Maxim's (formerly Dallas Semiconductors) DS18B20 is a great, low cost chip for measuring temperature.

As it is using the 1-wire bus and protocol, that requires a single pin on the microcontroller and thanks to the individual 64-bit addressing of the chips, the protocol and bus supports several DS18B20 sensors to be connected on a single pin.

The chip operates between -55 and +125 C and is accurate to +/-0.5 C over the range of -10 to +85C.

Wiring the DS18B20 is simple, see this great article.

Each sensor is identified with a unique with the 64-bit chip address. To find out addresses on the bus, you can use the Node's serial console (via the Arduino IDE's Serial Console) as the Node will enumerate and print addresses on each pin specified as a 1-wire bus. Optionally, if you have the skills, you can also use this guide.

DS18B20 Datasheet (PDF)