Berkshire East Ski Area
Located in Charlemont, a really nice medium sized ski area.

Blandford Ski Area
A reasonably priced small ski area, about half an hour west of Springfield.

Bousquet Ski Area
Small ski area in Pittsfield with good prices (21 trails).

Brodie Mountain
Excellent medium-size ski area in New Ashford (40 trails). They also have Cross-country skiing.

Butternut Basin
In Great Barrington. They have a really strange "triple chairlift." Nice ski area.

Catamount
Another ski area, located along the New York border. I've never been to this one, but I've heard it's good.

Jiminy Peak
I remember having a great time at this place when I was a kid.

Otis Ridge Ski Area
Small Ski area in Otis.