I am a United States citizen traveling to Canada, do I need a passport?

No, you just need two forms of ID, like a driver's license and birth certificate.

I think so, since 9/11 al the rules changed

I heard just recently that we will soon need a passport or maybe we do now already. I would check into it by calling official people to find out.

No, but if you don't have one, then you need to bring another document that shows your proof of citizenship. If you were born in the US, then you need your birth certificate. If you were born outside the US, then you need your natrualization certificate.

You do NOT need a U.S. Passport to enter Canada UNTIL March 2007. At present you need two forms of government-issued identification (i.e. driver's license, birth certificate). Happy traveling in the Great White North!

Presently U.S. citizens do not need a passport to enter Canada. However, your government is working on a bill that would require both U.S. and Canadian citizens to present a passport at border crossings. If passed, it would take effect in 2008. Until that happens, any type of document showing that you are a U.S. citizen will allow you to enter Canada.

as of December 2006 you will need a passport until then you do not but be prepared to encounter many problems with Customs agents as they prefer travellers with passports. Since 9/11 it has been the norm to travel with a passport no matter where you go

I don't want to miss a thing here so I need to copy the one I've searched that perfectly don't give you any doubt..and the website is the complete information.

No. Americans do not need a passport to visit Canada. However, the Western Hemisphere Travel Initiative (WHTI) will require American citizens to present a passport to cross the Canadian border beginning January 1, 2008.
For now, if you are an American citizen crossing the border into Canada, you need ID that proves two things: 1) Citizenship, and 2) Identity by way of a photo.
A driver's license on its own or a Social Security Card on its own are not valid ID to cross the Canadian border.
The following pieces of identification will serve as satisfactory proof of American citizenship to enter Canada:
US passport
Birth certificate,
OR
Certificate of citizenship or naturalization,
Photo ID, such as current driver's license

My advice is to get a passport now because you gonna use it anyways next year or so...
and to finish...I have a US citizen friend and travels everytime to Canada to visit his wife because his PR is not yet granted.

In 2008 you will need a passport to get into Canada.