Battery drain

Can anyone help us diagnose our problem. We have a 94 Mercury Sable and it keeps draining the battery. I had to replace the alternator and now, I don't think that might have been the original problem. I have noticed that the radio and windshield wipers will continue to run after the key is out of the ignition and in my hand. Will a faulty ignition switch cause this? Help, we are really getting upset with our cars!