Yes, when crossing the boarders to other countries, you always need a passport.
Yes
You don't need a passport because it is a cruise
If you are form Australia than no need to passport to travel < a href=http://www.cruiseeasy.com.au/>cruise Australia.
yes you need a passport to travel everywhere!
For travel by sea, you don't need a passport for re-entry to the United States but you do need some kind of documentation (see link below). If you are traveling by air, then yes you have to have a passport.
I am not sure either!
To leave the United States you would need a passport. This is also required for air travel, and land travel.
All cruise lines strongly recommend you get a passport, but it's not required for "closed loop" cruises in the Western Hemisphere. http://www.cruisesavvy.com/savvyguide/know_before_you_go/do_i_need_a_passport
Yes, you need a passport. When you travel to other countries by plane,car,ship you should always have you passport along.
Yes, when you travel to different countries you need your passport in hand.
If it involves going to another country, yes. And if your cruise lands somewhere other than Canada, Mexico, the Caribbean, or Bermuda, you'll need a passport book, not just the passport card. Source: http://travel.state.gov/passport/ppt_card/ppt_card_3926.html
Yes, you need a passport for a cruise to Canada.