People who are between midlife and old age are looking for another round of service with the same motivations that young people have--to give back, to have an adventure, to acquire experience, and to gain credentials and credibility.
Businesses in the same industry can be loath to work with competitors. But--as shown by the creation of All For Good, which aggregates volunteer opportunities from nonprofits all over the country--sometimes working together can result in more good than harm.
Most opportunities for service involve painting schools or serving food. But many Americans have skills--accounting, design, communications--that would be incredibly valuable for nonprofits and would make their volunteering more rewarding.