Go and visit a public garden. You can't believe the colors out there in the professional gardens, and you would be a fool to miss them. Philadelphia really is America's Garden Capital, with 30-plus public gardens within 30 miles of the city, and many of them cost very little or are free to visit. For those with a charge, watch their websites for discounts, days when seniors can visit free, and special events that are worth paying extra for.
Start some seeds of fall crops like broccoli, cabbage, and short-season cauliflower (that's seeds with 60 days or less to maturity). Just keep them on the windowsill where you can both keep them from getting too hot and protect them from the chomping bugs in the Great Outdoors. If you haven't got the space or the inclination, start watching for transplants in the nurseries in the next few weeks. These like to ripen up in the cooler days of the fall, so make sure to keep them watered and mulch them a light-colored mulch like salt hay or straw to keep the soil cool.
Keep up with the zucchini. Pick them while they're small: Squash grows very fast once it sets fruit, and a nice little pickle turns into a baseball bat practically overnight. And although they're very impressive to show your neighbors, they're just not as tender as the little ones, may need to be peeled, have very large chewy seeds, and are only good for making zucchini bread. This time of year, if the squash borers haven't got you, squash plants are putting out enough fruit that some of us are resorting to wrapping them in packages with ribbons and leaving them in unlocked cars in hope that someone will take them.