Twitter

What kind of information is being posted by the library accounts above? What kind of information should libraries post?

After looking at the library posts, it seems that almost without exception, we are posting about library programs and library and book-related current events.
I think that this is the appropriate kind of information for the libraries to be posting. The usefulness of Twitter comes from being able to provide information directly to your audience (people who choose to follow you), so it makes sense for us to be promoting our programming.
One area that I think we could improve on is in engaging with our followers. The endless stream of announcements and program info may get tiresome to some. Responding to questions, retweeting, asking questions, posting photos, links and the like may help us to improve the library's image and make Twitter a more useful outreach tool.