"Ca Roule" - for the non-Frenchified pronounced, "sah- (r)ool(h)"- was a great find and budget-wise was great for the pockets as well. There was one of many options of renting a super-comfortable ride (plush leather bottoms anyone?) but here are just 2 we considered:
1. Bike Tour: average price ~ $45 with tour guide and likely accompaniment of several annonymous tourists (good way to meet new people!), 4 hour trip total. They have set times that they leave so plan accordingly.
2. Half-day rental: For the weekdays, only cost $20 which was a great deal and what we ended up choosing. They provided a self-guided map and my friend and I ended up riding to/from Atwater Market for lunch, the Grand Prix stadium (which also has a beaautiful garden, a must see), and crossing the big bridge over the St.Laurent river (great view). All in all was a 4 hour trip, easy ride, probably covered at least 10 miles.
Best way to travel in Montreal, do as the Canadians do!