The site received so many hits it crashed yesterday, a site spokesman said.
So far, more than US$18,000 ($21,300) has been raised for them.
The site describes two kind, selfless people. Jessica Downes, 32, is from California, attended Johns Hopkins University in Baltimore and is a nurse at Massachusetts General Hospital, the site says. She is described as selfless and funny, but tough and confident.
Patrick Downes, 30, who has run the marathon before, is Boston through and through.
"He has that accent that makes it impossible to tell if he's saying 'parking' or 'packing', he's no more than two degrees of separation from Whitey Bulger (or so he claims), and he cried his eyes out when the Sox finally won the World Series," the site said.
He graduated from Boston College and was "nicknamed 'Jesus' in high school for his goodness", according to the site.
"She has the spirit of a lion, and combined with Patrick's good (the most good!) heart and interminable support for his wife," the website says.
"I have no doubt in my mind that they will persevere through this horrific time and will soon enough lead happy, normal, fulfilling lives."
- AP
