I've always been impressed by food cart culture in Philadelphia. I think they have the best and most diverse range of food carts of anywhere that I've visited. The food cart scene is best on the U Penn campus, particularly around the medical school. I was always impressed by the carts that offer bowls of fresh fruit, but you can get all sorts of international foods in a very small radius.
My colleague Rajeev Alur took me to his favorite, Magic Carpet Foods. I had the Dervish Delight, which ncluded falafel, hummus, taboulli, tossed salad, and pita. The proprietress was extremely nice and explained my choices. She recommended sesame seeds, which were wonderful. The falafel, hummus, and taboulli were all of excellent quality. The range of textures and tastes in this style of food is a constant source of enjoyment. Rajeev is a regular at Magic Carpet and if I lived there, I would be too.