Volunteering offers great opportunities to help out in your community as well as create new social networks, roles and outlets. You get the chance to meet people from all walks of life and to make a positive change.
If you want to work with children and teens, you can get involved with a local literacy program that works to improve kids' reading levels. There are also "foster grandparent" programs in which you can work directly as a friend and positive role model for at-risk youth.
Other seniors need your help as well. The Senior Corps is a program that connects senior volunteers with those in need (including the foster grandparent program). It offers the a senior companion program that lets you help other seniors with household chores, shopping trips and medical appointments. You could visit or volunteer at nearby retirement homes or deliver food to the homebound through the Meals On Wheels program. Households in your own neighborhood may need a little relief as they struggle to provide home care for a disabled relative and would likely welcome your offer to sit a few hours with their loved one so that they can run errands.
Volunteer help is always welcome at community soup kitchens, thrift stores and various outreach programs for the homeless, although opportunities can also extend far beyond your ZIP code. The Peace Corps, for one, welcomes retirees.