Another Very Important Thing About Traveling to Canada: Make sure you bring both your picture ID and a certified copy of your birth certificate (or your passport, if you have one) with you to the border. Customs agents on both sides of the US/Canadian border can and will ask you for these things for identification.
My friends and I were very surprised when we were not asked for our ID when we entered Ontario from Port Huron, Michigan, on Friday night -- but we had to show our driver's licenses and birth certificates to the US Customs agent when we returned to Port Huron yesterday afternoon.