If you're still interested, National Semiconductor used to make a broad line of analog ICs at a reasonable price, including a cheap, 4-pin temperature sensor called a LM20. Since Texas Instruments bought out (and destroyed) this excellent company, you have to deal with them now. Try this link:
Temperature Sensor Eval Board
It contains three sensors, and connections to the outputs of each. There are also links to application notes, which usually offer complete reference designs free for your use.