First of all, your best strategy is to sit tight and wait for the ice to melt away. Later you should focus on preventing future dams by making the improvements described at. http://www.thisoldhouse.com/toh/article/0,,1131314,00.html

If you really, really can't stand just waiting it out, here's an ice-melting tip courtesy of This Old House: Cut the legs off a pair of pantyhose, fill with calcium chloride ice melter and lay them down the slope of the roof so that each leg crosses a section of ice and the toes dangle over the edge of the gutter. This should melt small channels in the ice, allowing runoff to occur.