I've failed to open my faucets to leak during the cold night. I've been without water for a day. Pipes still frozen. I have a heater under the kitchen sink and a heater in the garage where the water heater is located (closeted area). I've also slightly cracked open the faucets in the house. Should I shut off the main water supply leading to the house?

Won't hurt. Prevent flooding when pipes thaw if a pipe has burst. Doesn't do any good to have the water on if pipes are frozen.

Is the main frozen so that you have no water? If so, locate where it comes into the house and use a hair dryer to warm it up. Open up the first cold water faucet after the main comes into the house. Do you have a water flow? What have you done so far? You have any more details you can give? Back to you, Tom