Have a look at: http://thermistor.sf.net
It will teach you about the equations, coefficients, and has some code to calculate the coefficients. I did this with my 2 salvaged thermistors and it works very well so long as I use the full Steinhart-Hart equation.
You can also have a look at the library I added to the playground:
http://www.arduino.cc/playground/ComponentLib/Thermistor4
I have a lot of documentation in the source that will probably answer most questions.