There are alot of Arduino + temperature sensor tutorials out there, but what makes this one different is the use of the DS18B20 sensor. Each DS18B20 has a unique 64-bit serial code, which allows multiple DS18B20s to function on the same 1-Wire bus. Thus, it is simple to use one microprocessor to control many DS18B20s distributed over a large area.
In this article Bildr presents the code and circuit diagram for interfacing one DS18B20 with the Arduino. This project requires you to have the “One Wire” folder in your Arduino Library.
Someone should really edit that Arduino playground page and remove all the ancient versions. Everything before version 2.0 is horribly buggy.
There is a little community of users who use the one wire parts for weather stations. To get a flavor of what is happening check out http://www.weathertoys.net.