Oh sure, NOW you go to Philly when I no longer live there.
But seriously, check out South Street. It's a fun strip o' quirky shops 'n what not, and the Jim's Steaks place there has some o' the best cheesesteaks you'll find in the city. Of course, a lot of people will also tell you to check out Pat's or Gino's steaks which are right across from each other.
Also be sure to check out the Mutter Museum. It's a museum of medical abnormalities and death! Perfect for viewing right after you've downed a few cheesesteaks.