zoltn_p
  Junior Editor

To my knowledge:
'naught' in USA: Old/archaic version of 'nothing'. Only really used in some phrases.
'naught' in the UK: Old/archaic version of 'nothing'. Not used often. Mostly in places where you want to use "polished language".
'nought' in the UK: Means zero and I hear it in everyday speech, even if not very often. Also used a lot in maths/sciences when reding out numbers.

Note: I have no experience whether and how often nought is used for zero in the USA. more »