I suggest Le P'tit Train du Nord, a very nice rail/trail going northward beginning in the northern suburbs of Montreal. When I did it 6 or 7 years ago, there were shuttle services who would transport you and your bike from one end to another for a very reasonable price. It was 125 miles/200 km long when I did it, but I believe an extension southward toward Montreal has been built adding another 19 miles/30 km.

http://www.laurentians.com/parclineaire/