Many sick, injured or elderly people find it difficult to take care of even the most routine errands. Often, able-bodied adults volunteer to drive them to appointments or assist with tasks like grocery shopping. Parents that participate in one of these programs can check into taking a child along for the ride. Often, a kid or teen will add a little excitement to otherwise mundane errands and will probably feel important just for being included. Make sure it's OK with the person you're assisting, though, as he or she may prefer a quiet ride without children.
Similarly, many organizations and churches provide meals to people that can't cook for themselves. Simply sign up for a regular meal and have your child help you prepare and deliver it to a grateful recipient. Just don't forget the dessert!