Our own supercharged Jon L points out Zafar Shah's really pretty useful introductory article, What's a Blog, and Why Should Nonprofits Care?. If you are trying to get folks at a cause you care about to adopt new media tools, this is a pretty good article to hand 'em.
"More typically, an externally focused blog can transform informal knowledge sharing into a new asset for an organization. Blogs can enliven your group's Web presence and engage clients, supporters and strangers alike in your work. 'We think that there is a good chance blogging is a new way to express the nonprofit voice,' says Jim Fruchterman, CEO of Benetech, a nonprofit organization that puts technology to work for social needs. 'We feel we have unique things to say, so we should be saying them.' "