That's very nice. The American Cancer Society has ways to volunteer http://www.cancer.org/Involved/Volunteer/ or you could contact them (1.800.227.2345) for help with that.
Or you might check at local hospitals or cancer centers to see if they have support groups and volunteer opportunities.
If you're social, maybe think about starting your own little support group. There are free websites like meetup.com that facilitate people getting together that share similar interests.
A few places to start.