Yes, a passport is needed as 2009.
No, a passport is not needed. Vancouver and Regina are both within Canada.
No, but you should have a picture ID.
US citizens require a valid passport to travel to Canada. They do not need a visa.
No (but valid photo ID is needed if flying)
no, if you aren't leaving the country no passport is needed. It is a good idea to have one if you are travelling because it is a generally accepted form of id.
Yes. It is now (for about the last year).
Ideally a passport.
A passport is needed to cross any international border.
To get accross the border to travel to Seattle from Canada, a passport would be needed. Traveling via plane to Arizona would also require a passport, since the person traveling is a Canadian citizen.
If you drive through Canada it is.