After I became my colony's Philanthropy Chairman last year, I became really involved with one of our service projects, the Eating Disorders Coalition of Tennessee (
http://www.edct.net), which works to create eating disorders awareness and prevention. It is a grassroots organization, and I am part of their Community Development Network (main Memphis organizers; there are about 10 of us).
Even though I am no longer Philanthropy Chairman, I am still working with the EDCT. My advice for people who are interested in advocacy is to find something you are passionate about (ie, helping people struggling with eating disorders) and work on the grassroots level. It is a great way to get involved!