I picked Pintrest for this one. Mainly as I have always wanted to try it but never got around to actually using it. It kind of reminds me of a highly arranged and organized scrapbook. Only online of course.
I noticed other libraries have added book recommendations and the like. This could be a good way to keep your patrons informed on new and popular titles in the collection. Hand out the library's Pinterest URL and patrons can see what is available.
Additionally you could bring up items for discussion at your library. Say you wanted to have some sort of program where people could come together to debate certain topics. This would be a good place to start. Check out this banned books site, which is very relevant to those who have ever worked in a public library before: When Banned Books Attack!
This is also a helpful tool for looking for others online who may share your weird hobbies or passions. Here is a person who appears to love Yoda as much as I do! Yoda he is! Talks funny he does!