Hi I'm am married to a canadian citizen as of July 2008 and he never lived in US or worked in US at any time. I was wondering if I should file married separate or file jointly? And what form should I use?

If you are a U.S. citizen or resident, you can file joint return as residents. You must both report your worldwide income for the year.

If any one of you have any foreign income, and on that income you paid taxes in the foreign country, then you can claim foreign tax credit (Form 1116) or you can use Foreign Earned Income Exclusion (Form 2555). Read: Your U.S. Tax Return: U.S. Citizen or Resident with Foreign Income