Civic engagement and advocacy information from Independent Sector, a national organization of nonprofits, funders & business members—and an argument for it from a prominent funder (2 links):

http://link.independentsector.org/m/1/82346540/02-b17200-cc96dd2eb57f4523a70f952b83d97b13/10/446/0612c413-d5d3-4848-a1f0-9a270aa90bcb

http://us5.campaign-archive1.com/?e=c43990c969&u=86ea69664802a0541ae4385f8&id=2b1d85aa64