People from Boston & New England in general

My friend and I made a goal to do one 5k or 10k a month May-Nov. Does anyone know of any fun ones going on anywhere in NE? We're in Boston, but are definitely open to travel - in fact, that's better!
So far we have:

May - Run for Your Lives 5k
June - Will Run for Beer 5K
July - Harvard Pilgrim 10K at Patriots Place
November - Cider Mash 5K

Something with a gimmick or costume is ideal.

ALSO if anyone goes to any amazing fitness classes in the Boston area, I'd love to know as well!!!