My air conditioner stays on even with keys out of ignition?

When you say a/c is on, do you mean the blower inside the car is on, because unless the engine is running the compressor will not turn and give you cold air. The blower resistor is probably bad and creating this condition; or the a/c switch may need to be replaced. Unplug the fan control switch, if the blower keeps running, look under the dash, passenger side and look for the blower motor, find the resistor and check it, it probably has shorted out. If you don't know how to proceed, then get professional help, to avoid creating a bigger problem.