Temperature measurements were done with Thermistors successfully for many years prior to integrated devices that automatically return Temperature...
I remember a page from PH Anderson http://www.phanderson.com/picaxe/lin_thermistor.html that provides both the math, a table of values and much other useful information for efficient use of thermistors on both the PICAXE and the Arduino... With minor changes nearly any thermistor can be used and are generally much lower in price than many "sensors" (Linear types... LM34 centigrade, LM35 Fahrenheit, TMP36 Deg C, LM335, Deg K),
( Digital types DS18B20, DHT11 / 22 Deg C and RH and a bunch of other digital types as well from National/Ti)
While the analog or digital devices are accurate and easy to use they can be a great deal more expensive than a simple thermistor..
For that matter a silicon diode can also be used... I used a 1N4148 or a PN2907 BE junction for several commercial designs I did about 10 years ago... It did require an Op-Amp and a couple of pots but it was cost effective compared to a thermistor and the support electronics provided 3 point calibration which if carefully applied can be easily 1 - 2% accurate.. I used them (diodes with an analog LCD panel meter IC. an ICL 7105 and a bare LCD display as the 7105 was the LCD controller and A/D conversion circuit too.
I've used all of them at one time or another and found them all most useful...
I don't recommend the Analog types as most except the diode or thermistor generally are 10mV/Deg C and that's a half a bit or 4.8 MV.. The issue is complex but breaks down to the A/D converter not having a separate Analog return so it does have some.. Digital noise issues and the LSB frequently is a throwaway because of the induced digital noise both from the digital ground loops and the lack of real filtering on the AVcc supply.. 100 nF is barely adequate... but you should have no real problems past the LSB bobble...
Perhaps the best part is that there isn't a special library required for the thermistor and it can be assembled for less than a dollar with equal accuracy as the integrated devices... Good education too...
Doc