For Those Who Pray Regularly or on a Schedule, What Happens if You Forget or Skip a Prayer?

Muslims have scheduled Salat prayers 5 times each day; devout Jews are told to give thankful prayers 100 times each day according to the Talmud; and Catholics have days of Holy Obligation on which they are supposed to attend M. Whether you practice one of these traditions of scheduled prayer, or another one, what do you do if you skip, forget, or otherwise miss a prayer? Do you owe a prayer? Can you make it up? Is there a penalty prayer or penance that you do? Thank for your thoughts!