I work from home most of the time, but go into the office every now and then and when I ride in, I bike from Maple Shade to 6th and Market. I'm sure you are looking to go a bit more south than that though.

Check out these maps from the Bicycle Coalition of Philly http://www.bicyclecoalition.org/resources/maps

They should give you an idea of bike friendly roads in the city.