I do not know of a law in MA that specifically prohibits cyberbullying or bullying.  However, in extreme cases, another law may come into play, such as laws against criminal harassment and stalking (Massachusetts General Laws Chapter 265, Section 43a and 43), and victims may have civil recourse through law suits.  Attorney General Martha Coakley has said:
 
"Electronically-communicated threats are a crime in the same way that a face-to-face or written threat can generate a criminal charge.  Willfully and maliciously directing electronic communications at a specific person that seriously alarm that person and would cause a reasonable person to suffer emotional distress can result in criminal charges as well as generate a lawsuit seeking financial compensation."
 
I would certainly check with the administration of your daughter's school to see if the school has any policies in place (especially if the bullying is occurring on or originating from school grounds).  Good luck, and please tell your friends about The Forum.
 
Update (3/6/10):  Legislators to debate anti bullying bill:  http://www.mass.gov/legis/bills/senate/186/st02pdf/st02283.pdf
Update (4/28/10):  New law passed:   http://www.thebostonchannel.com/politics/23309527/detail.html