What's the purpose of the resistor in this circuit?
jgrahamc: As others have pointed out this is a voltage divider.  But what's not been pointed out is that this type of voltage divider is not ideal because the load applied to the output voltage can alter the voltage itself.  It's very important that the load applied draws very little current (i.e. has a high resistance/impedance) otherwise the voltage divider's output voltage changes.The best way around this is to use a voltage divider to produce a reference voltage and feed that into an op-amp that adds the reference voltage to the voltage coming from the device to be measured (in this case the thermistor).As an example of this see my blog posting on building a temperature probe for the OLPC: http://www.jgc.org/blog/2008/03/building-temperature-probe-f...