Food Carts, Rittenhouse Area
I work in the Comcast Center and while the Market is wonderful (esp. DiBruno's for a splurge) I'm really interested in exploring the many food carts in the area - can't beat lunch for $5. I'm a regular visitor of the falafel cart at 16th and JFK, but would love to hear some other recommendations for carts to visit in the area.
Clearly, you should be going to the falafel cart at 20th & Market instead. :) I'm only half kidding; I do prefer that particular cart's falafel best.
Otherwise, I'm inclined to say that other than the odd fruit carts, the area where you (and I, actually) work is just devoid of a variety of cheap lunch options.
I work in that same vicinity. I tried several of the Chinese food carts and they are just awful. My favorite reasonably priced lunches are: takeout from Pikkles Plus (great corned beef sandwiches, burgers, cabbage soup), takeout from City Garden (vegetable fried rice & wonton soup), slice of pizza and half salad from La Scala (they don't have the half salad on the menu but they will make it for you half price of regular salad). For more cheap lunch options explore inside Suburban Station itself which is a little more downscale than the Market. If you are in the mood for a long walk to Rittenhouse area, takeout from Tampopo is good (bimbimbop, rice bowls). If you want something light, ry Au Bon Pan for soup or salad and fresh bread. Of course there is also Cosi and Corner Bakery. Its a pretty good variety of semi-cheap lunch options, but not dirt cheap.
I like the hot dog cart at 17th and Market just outside of Liberty Place. They grill the dogs/sausages instead of dirty watering them.