Driving to Canada

I have a temporary visit visa to Canada till 2008. I am currently in the US and am an Indian citizen (I have a B1 visa for the US). I am in the US till October 5th 2007. I am currently using a rented car in the US. I was planning to drive to Canada from Baltimore, MD in September 10th 2007. Is this possible? I would stay just for a few days in Canada at my uncle's place (who is a citizen of Canada). After that I would be back to the US and then return my rented car in the US after my stay here.

Please let me know in case I need to carry any additional documents or if there are any hassles involved.

Thanks
Santhosh