Originally Posted by sitzmark .
Welcome Salesman.
Haven't done the canal in a couple of years, but used to inline skate it regularly. From end to end it is about 7 miles - so about 14 miles round trip. Often frustrating because you can get head winds on the way out and on the way back. Very smooth and well maintained surface (blacktop). As noted it gets very crowded on nice warm days - especially weekends. Start early and it is not too bad - after 10am or so it gets busy, busy - some people wander in fog, not paying attention to bikes and skaters, so you need to be always on the lookout.
There are two paths - one on the north side (Buzzards Bay) and another on the south side of the canal. The south side is a little shorter, but also less busy.
A similar ride (but one that is not closed access) is the East Bay Bike Path starting around India Park in Providence to Bristol, RI. 14+ miles end-to-end - 28/29 mile round trip. Generally less congested than the canal, but still busy in many sections. Again, the earlier the better.
Farther north is the Blackstone Valley path along the Blackstone river - 11 miles end-to-end. Woonsocket, RI to Valley Falls. Eventually the build out of the path will be 48 miles from Worcester, MA to Providence, where it will connect with the East Bay path. Only the Woonsocket- Valley Falls section is complete now.
If you're new to cycling, these are excellent places to start. Cape Cod canal is fully isolated from auto traffic. The Blackstone Trail has a few road crossings. The East Bay path has a number of controlled crossings and side roads.