I get mine from a place that loans money, they have a big sign in their window that says Money Order 5 cents. If I don't have time I go to the grocery store and they are .65.
I buy stuff on e-bay and sometimes they only want Money Orders.
Check Cashing places. I don't know if these places have the same name outside of NY. They are places that cash checks for people that don't have checking accounts, you can also pay phone, cable, gas bills there.