As of July 2008 - Not for a US citizen, just a birth certificate and a government issued photo ID, such as a driver's license. Other nationalities are required to have a passport. no. you'll need a government issued photo id. you will need your birth certificate also to get back into the us. however, a passport would make things easier.
when does a us citizen need a passport to drive to Canada
yes
No, you cannot enter Canada with an expired US passport. You must have a valid passport to enter the country.
yes, all entry into Canada is required to have a passport, you'll need it to re-enter the US anyways.
yes.
That would depend on your nationality. If you have US or Canadian citizenship, no, you just need some ID (such as driver's licence). For other nationalities, you may or may not need a passport. Eg, for Norh Koreans, they would need their passport :-)
as of June 1st, yes. You'll need it more for your return to the US then anything else.
Yes you do now if you are flying. EDIT : As of January 2008, you will need your US passport not only to enter Canada, but perhaps more importantly in your case, to re-enter the US. Passports are need tofly to and from Canada, but not for LAND or Sea travel until June 2009. See this site. http://travel.state.gov/travel/cbpmc/cbpmc_2223.html
Yes, any visit, no matter how short or long is required to have a Passport to enter Canada, same goes for the US
When you are not a citizen of the USA a passport is usually required to enter the US. However, for many years citizens of the USA, Canada and several other western hemisphere countries did not need a passport to enter the US. Because of increased security procedures, even US citizens must have a passport or passport card to reenter the US across the US-Canada land border or by sea from the Caribbean after 18 May 2009. Passports have been needed for all entrants by air for a year before that.
Even Infants can enter the US with their US passport. So there is really no age limit to one who wants to enter as long as they have appropriate documents.
I am tempted to respond by saying that I don't need a passport for anything that you do. However ... You do not need a passport to enter Canada, but you might experience difficulty getting back into the US without one.