You can get the latest code from the github repository at https://github.com/adafruit/Sous_Viduino
There are several versions of the DS18B20 library out there. The code for this guide was compiled with version 3.7.2 which can be downloaded here:
Dallas Temperature Library
And the PJRC version of the OneWire library
Douglas Baldwin's "A Practical Guide to Sous Vide Cooking"