Every time I have driven to Southern VT., it has taken 8-9 hours. Yahoo maps says that one can get from DC to Mount Snow in 6 hours and 53 minutes. That seems optimistic. Mount Snow is probably the closest big Southern VT resort near DC. It's a great place for intermediate cruisers: lots of broad, moderately pitched boulevards. Stratton Mountain is similar but with a tad more vertical (2000 ft versus 1700 for Mt. Snow). Stratton is owned by Intrawest and has a nice slopeside village.
To compare the mountains, go here: