An article about Blogging at Your Library...but this really applies to lots of other organizations as well:

So why are blogs important to libraries? In one word%u2014communication. You can reach your patrons or staff in a whole new way. Information can be posted instantly. You can highlight an event in your community, review a book, or announce new materials. A blog gives people a reason to continually return to your site. Parts of your Web site can be blogs. Pages that change regularly can be quickly updated if they%u2019re a blog and you don%u2019t need to know HTML. Each department can update its own page. You can also communicate easily with your staff. Everyone from the director to part-time staff can post policy changes, news, or vacation schedules.