In the spirit of MLK Day of Service, I'd like to throw this question out there. You may have a particular charity that you donate to regularly, or an organization in which you volunteer when you are able. Either way, you're doing your part.
But what if you don't have a particular charity that's close to your heart, or you don't volunteer at a non-profit organization? Take heart, there's always something you can do. Check in on your elderly neighbors when it's bitterly cold or blazingly hot. Visit them regularly to see how they are getting on. Write letters to your local service people to let them know you appreciate their sacrifice. Your teenage children may have friends that ask advice on their future career. Answer their questions or offer to introduce them to contacts in their chosen field.
Charity most often begins at home. Take time to sit down to dinner each night with your spouse and children and discuss the day's events. Relax with your dog or cat to give them some attention. If you're a runner, think about entering a local race to benefit charity (and get in shape). Most importantly, call your parents, if you are still fortunate enough to have them in your lives.
My modus operandi with my clients is to first do no harm. After hearing the facts of their cases I ask, what can I do to improve this situation or, what can I do that won't make things worse. Perhaps that's a good metaphor for life.