This one required some thinking about what the routes are actually called. In rough order of when I first took them:
Carolinian
Adirondack (beautiful but sloooooooow)
Vermonter (back when they ran a bus between Montreal and St. Albans)
NE Regional (as far south as Lynchburg, as far north as Boston)
Piedmont (2-3 roundtrips a week these days)
Lincoln
Crescent
Acela