From West Cambridge, Arlington:
Harvard, hacked from memory and Pamela Blalock's route.
South Chelmsford, an evolving route in part based on one of my first rides in the Boston area.
Expanded Concord, Carlisle ride with as much off the main road travel as feasible in a 2.25 hour ride from Arlington center.
A 60 miler from Arlington and staying inside of 495.
A 50 miler that takes you over Nagog Hill Road in Acton.
An 18 mile loop north from Concord that keeps you off of the busiest roads when possible.
Tripoli Road and Thornton Gap - do this ride in reverse and you will get a long, generally downhill run.
Western Massachusetts out of Ashfield but you can easily start in Conway, or even Williamsburg.