This is a place I have always wanted to go for a run and managed to do it today (10/29).
The Visitor Center contains a graphic for trails and so does the linked site below along with a link for the Blackstone Corridor. This is a great scenic area as you have one trail system that goes along the river and another system that is used for a tow trail for the barges.
There is also another park in the area that I will explore after hunting season (10/15-01/31/10) and that is the West Hill Dam only about a mile away.