I know that there is a bike trail in Montreal near the Lachine Canal.

Also near Quebec City, the Isle d'Orleans would be great bicycing.

http://www.mcgill.ca/rethink/what/transport/ Link to a bicycle map.

http://english.montrealplus.ca/portal/feature/8536/2.3.jsp

A general page that includes bicycling: http://www.out-there.com/tpq00trm.htm

Frances Toronto, Canada