Starting January 31st 2008 if you are driving to Canada you need a Goverment Issued ID with you. To prove that you are a United States Citizen.
Starting June 2009 however you WILL need a passport to drive to Canada.
I found this information on http://www.corporate.canada.travel
Im going to assume this is updated information. I found it through Yahoo.
Anyways so this is good news for me. Because that only means that I'll be going to Anime North ^^
If anyone has anything contradicting this let me know. Im hopeing this is right. Im going to keep looking though just incase ^^;