If you have ever wondered what Twitter is all about, or tried to explain it to someone else, this is a great place to start.
Twiter in Plain English
Another great explanation video from CommonCraft: Twitter in Plain English. Twitter seems to puzzle many people, micro-blogging, useless "lunch was good" updates, and so on - so this would be a great way to show you staff how exactly this tool works. Then follow it up by showing them how libraries are successfully using Twitter to do various tasks.