I love 1-wire sensors now that I have used a few with Arduino controllers.
A generic product page:
1-Wire Devices - Maxim
The DS18B20 is the temperature sensor that is so popular. Besides being a thermometer, you can tell it to be a thermostat, also. They are available in a waterproof package with 1 meter pigtail leads attached for $2.00 or less on ebay/amazon.
The thing i like about the 1-wire sensors over the linear sensors is that you can run a dozen or more sensors all off one line. With the linear sensors, a separate line must be run for each sensor, plus they need to be fed power. If you want to modify something, just splice in or remove a sensor from the data line. The 1-wire sensors can be fed power thru a separate line, but all they really need is a data line and a ground. They grab power for themselves off of the data line while it is inactive.