Mum - anywhere but Northern cities - we say Mam. Or Mammy when you're young (or young at heart like me) hehe

mum, mam, mom all may be used like Craig said. two more things. 1. Mum as a proper word means silent. 2. do not confuse mam with ma´am which is an abbreviation of madam.

In the states, we mostly say "mom," which is like "mah-m". Or "Mommy". I always thought it sounded strange to hear British people say "mum," but like Aseer says, that might sound like "ma'ame," depending on one's pronunciation.