We have visited the elderly in a nearby retirement community. We have spend a couple of hours at a food bank, sorting through donated boxes and cans and packing them up to be distributed to the needy. One of the things to consider is the comfort level of your young people with community service. If your youth groupers are younger, or are new to the whole idea, you may want to give them a more hands off project like making peanut butter and jelly sandwiches for the homeless. These sandwiches can then be donated to a local soup kitchen.
Students get the opportunity to perform mitzvot without having to confront the problem head on.
For the older kids, you might want to have them take the sandwiches and hand them out at the soup kitchen. Another thing that many youth group members enjoy is playing with children, whether they be at a hospital, at a shelter for abused women and their children or at a nursery that cares for youngsters who are HIV positive. We have these types of activites with great success. Our shul - congregation Ohr Chadash is new. We are made up of approximately six families who regularly attend services on Shabbat and Sundays, but we have maybe 60 families that call themselves members.