Women in Engineering initiatives; in Australia, only 15% of Engineering graduates are female. My organization runs regular programs to provide support and encouragement for women working in a primarily male field.
Cisco runs many event annually for CSR and encourages employees to spend a day a quarter (fully paid) to join one of our initiatives like helping out with Special Olympics whether helping as a volunteer or having a charity dinner to donate money to the cause.
I've worked on the delivery of an awareness project to promote Disability in the workplace. There's plenty of opportunities to volunteer your time for disadvantaged groups.