If you are considering adding a blog to your library site, this BBC article may give you the push you need: Blog Reading Explodes in America http://news.bbc.co.uk/1/hi/technology/4145191.stm .
And wouldn't you know - there is a great blog about libraries using blogs:
http://www.blogwithoutalibrary.net/ .
There is also a book on the subject (but I am not sure if this blog is listed-grin!). Review here:
http://www.freepint.com/bookshelf/weblogs.htm
Using a blog to serve our users is along the same lines as having a phone for them to call us, a web site for them to access the collection, an email address for them to contact us...