‘I can’t find my Phone‘ and ‘Where’s my CellPhone‘ are two web Services which helps you find your missing cellphone. You kept your phone somewhere and later forgot where you kept it. In this situation you will then ask someone near you to make a call to your phone. So that you can find the missing cellphone by hearing the ring sound.
But In case no one is around you. These websites shall help you. Goto any one of them, enter your CellPhone Number. Click on the dial button. The web service will make a call on your number. This is totally free. But currently both these Web Services only works in US and Canada.