Jiminy Peak (Massachusetts/NY line) is open until 10:00 at night. Not the biggest mountain -- about 1200 vert -- but I don't know of anyone else open that late. They used to let you stay all day with a regular lift ticket, but now they sell tix in 8-hour blocks. We went Sunday...pretty fun place. They even have the east coast's only "mountain coaster," a roller coaster built right into the mountain side. Not an alpine slide, an actual metal-rail roller coaster, and it's open during the winter. Fun little mountain!