In addition to the many sightseeing tours of Independence National Historical Park [1], the following tours are available for those looking to get off the beaten path and explore other areas.
Links:
[1] http://www.moon.com/destinations/philadelphia/discover-philadelphia/explore-philadelphia/sightseeing-tours
[2] http://www.moon.com/destinations/philadelphia/arts-and-leisure/recreation/guided-tours/i-glide-tours
[3] http://www.moon.com/destinations/philadelphia/arts-and-leisure/recreation/guided-tours/philadelphia-preservation-society
[4] http://www.moon.com/destinations/philadelphia/arts-and-leisure/recreation/guided-tours/poor-richard-s-walking-tours