There are probably a dozen trails that converge on this trailhead, including Sylvan Way, Valley Way, Brookbank, Airline, The Link, Brookside, Inlook and Amphibrach. The Randolph Mountain club is to blame for the profusion. They publish their own map which you can find at http://www.randolphmountainclub.org/stuffwesell/trailmap.html ; most other maps (even the AMC maps) are not really complete.
Charles is quite right about the crowding; in summer it's common for cars to park on the shoulder outside the parking lot.