I'd call this an Intermediate area, nothing terribly technical, but the trails are very nice! There's some good climbs complimented by some fun downhills. Overall a good place to hit a ride after work, or to get your feet wet.
From Route 3, take exit 1 west on Spit Brook Rd. Split Brook will turn into E. Dunstable Rd. then Lamb Rd. Take it until Lamb Rd until Ridge rd splits off to the right and take that until you reach Main Dunstable Rd (111A) and take a left. Go about a half a mile and you'll see a softball field on your right. Park there and ride away!
http://www.singletracks.com/item.php?c=1&i=4954