I just stumbled upon Bikely.com - a web site that "helps cyclists share knowledge of good bicycle routes". The web site combines Google Maps with user-submitted bike routes.
A search for Ottawa bike routes brings up nearly 50 routes so far, like the Ottawa Pathway loop and the Ottawa-Gatineau Bridge Tour.
Fall, by the way, is a great time for cycling in Ottawa. My favourite fall route is this one through Rockliffe, and heading east along the Ottawa River.
Related: Ottawa Bicycle Guide