Careful of the MPs on the base, you aren't supposed to be there. Great biking to train close to Burlington.
Off northbound exit on I-89 take a right on Rt. 7. At second light take a right. When road takes a sharp right, there is a Colchester Town Park. Follow gravel doubletrack and head into the woods on any singletrack.
http://www.singletracks.com/item.php?c=1&i=516