The Kennedy Food Garden is probably the best small grocery store I've found in Center City, and I'm sad that we don't live near it anymore. They have a really wide selection of your non-perishables (crackers, cookies, pasta, cereal, canned goods, jams, etc) and kosher food, a great selection of dairy and bread (fresh made and pre-sliced packaged), but best of all, their produce is always, ALWAYS fresh. I've never seen a place this size that has fresh, varied produce before. Their deli is top notch, and I think the prices are reasonable for a local grocer.
If you live nearby, this place will probably have what you need and save you the trip to a bigger store when you're in a rush.