Thermocouples are typically used to measure high temperatures, like
exhaust gas temps.  a JK thermocouple sells typically for about $10-$20.

Thermistors and regular silicon diodes are better at the temps your talking
about.  You can even use a regular silicon transistor, and these all sell
for pennies.

these all change resistance with temperature, and the standard PC game port
has four time-based resistance measuring elements in it, perfect for this.

malcolm