The Deerfield River is perhaps the best coldwater fishery in the state, offering excellent trout fishing all year round due to cold water releases from the bottom of dams along the river. In addition, several tributaries, such as the North River, Chickley River and others offer excellent fishing for native and stocked fish. The lower reaches of the river downstream of Old Deerfield Town have great bass fishing and shad fishing in the spring.
You can access the river at several pull-offs along Rt 2 and Zoar Rd in Massachusetts.
There are several guide services in the area if you need some education before getting out on the river yourself.
Harrison Brothers: http://harrisonanglers.com
Arrowhead, on Rt 2 in Shelburne: http://www.arrowheadbaitshop.com