Ok, I lived in The Fenway. I would run from my apartment to the Massachusetts Avenue Bridge, up to the Larz Anderson Bridge (Harvard Boat House) down to The Museum of Science and back up to the Massachusetts Avenue Bridge. What an awesome run! I also lived in South Boston. The run up William J. Day Boulevard and around Castle Island is also one of the other great runs in Boston. So, that's my two cents. :)

As home to the world renown Boston Marathon, the city of Boston had it's share of runners. The city, however, is comprised on many neighborhoods--and each has its own places where one can run free. To name a few running (or biking) routes by neighborhood, try:

* West Roxbury -- Millenium Park
* Roslindale--Peter's Hill/Arnold Arboretum
* Jamaica Plain--Jamaica Pond and
Arnold Arboretum
* Hyde Park--Stony Brook Reservation
* Brighton--Heart Break Hill (Boston
Marathon
* Downtown--Charles River/Esplanade
* South Boston--Castle Island
* The Fenway--Emerald Necklace

This list should give you a 'running start'

Back Bay / Beacon Hill area. Here you are right along the Charles River. I am not a big runner and I enjoy getting out there once in a while! Its gorgeous.

Lots of options. Running along either side of the Charles is great -- you can do up to a 20 or so mile loop if you make it all the way to Watertown. The Emerald Necklace takes you to Jamaica Pond, and these neighborhoods are a bit more affordable than many others. One final suggestion - I used to live near Alewife, near the Cambridge/Arlington line. It provided great access to the Minuteman Bikeway, which was great for running and biking. See included link.