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[
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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.