Jeff over at Gather No Dust left a comment on my last post about Twitter saying the following:

"I was able to use twitter to send the library's rss feeds. Now anyone can sign up for library updates through twitter. When the library updates its calendar, announces events, or new books, it goes to twitter (and then hopefully, people's phones). Anything longer than 140 characters it turns into a tiny url for you automatically. Now I need to break it down for specific tastes (adults, parents, teens, children, etc.)"

Update: Thank you to Jeff, who posted an incredibly useful explanation of what he's done to make Twitter work with his library, along with links to a few other libraries using Twitter.