Flurry, NEFFA, Falcon Ridge? Pinewoods weeks? Peterborough Snowball isn't a weekend, but has as much dancing as one.
But, Julian is right that many dances in New England don't have their own weekend. Many of the larger dances elsewhere have one or even more weekend-long events a year, which draw dancers from farther away than usual, have higher-end calling and music, and build the kitty for regular dances. You'd expect there to be a dance weekend per week in New England at that rate, which would likely make them less successful as draws and fundraisers.
--jh--