Call 1-800-GOOG-411 (1-800-766-7411) for free business telephone number information anywhere in the US. This service also dials the number for you after you get the one you want.
Call 1-800-FREE-411 (or 1-800-373-3411) for free residential telephone numbers anywhere in the US. The draw-back is that you must listen to advertisements before you get your number. It will repeat the number (once the correct one is located) as many times as you say the command which prompts it to do so.