“Everybody’s on Twitter!” You hear that more and more often as Twitter gains adherents. Why, even the dead and the fictional (and the fictional dead) are on Twitter. Not to mention celebrities. (Let’s not.)

Despite having over 100 million registered users, it’s still small beer compared to other services. Facebook, for instance, has over 400 million. What’s surprising are the ways people, companies and organizations find to use the service. And who those folks are. Here are five Twitter accounts you might find surprising.

Library of Congress. Although the LoC has upwards of 53,000 followers, they themselves only follow one. The Law Library of Congress. They have books down pat. Not sure about electronic communications.However, as ReadWriteWeb reported earlier today, they’ve acquired the entire Twitter archive, so maybe they’ll pick up a thing or two.

Federal Bureau of Investigation
. Not too surprising that it’s the Press Office that’s Twittering. Fox Mulder might be off-putting to some, though possibly not as much as J. Edgar Hoover. At least these folks follow, although only a tenth as much as they are followed.

NASA. Lori Garver, deputy director of the National Aeronautics and Space Administration Twitters. And she does it right, mixing NASA news, issues of interest to space buffs and personal information. Well, mostly right. Honestly, Lori, there’s no one worth following but for two other NASA Twitter accounts? NASA as an organization Twitters its brains out.

The Tower Bridge. Inanimate objects Twittering is non-hilarious. This account, for a busy draw bridge in olde Londone towne seems on the level. However, it makes up for the unexpectedness of the account by the sheer almost operatic boredom of its Tweets. To wit: “I am closing after the Maintenance lift has passed upstream.” We can tell from the few accounts it’s following that the bridge has a real telescope fetish, though. Unseemly.

Ivy Bean
. Ivy has one unusual quality that makes her an unexpected Twitterer to most. She’s 104. Yes, years old. Participation of the elderly in social media communications is not that unusual. The young and the old are less fearless than the middle aged in experimenting with different ways to communicate. But 104. Holy Toledo. Some have suggested Ivy’s account was originally set up by journalists seeking “Digg bait.” Who cares? Ivy rocks the keyboard a year after her “story” was first reported. I hope I’m 104 when I’m her age.

For more, check out ReadWriteWeb’s Twitter coverage. Of course, there’s always @rww.