PHOTOS: Explosions Rock Boston Marathon

(Yahoo!) -- Following the deadly blasts at the Boston Marathon, acts of heroism were shared on Twitter and the Web.

Some runners who crossed the finish line continued running to Massachusetts General Hospital to donate blood.

Others on Twitter praised the first responders and marathon employees who tended to the injured.

Blood donors came out in force following the explosions. According to the Red Cross, their donations helped enormously.

For more on how to help those affected by the blasts, check out this list from Take Part.