WooHoo for Wikis!
I'm really impressed with the wikis I've found. I though the Book Lovers Wiki that's sponsored by the Princeton Public Library was such a great reader's advisory tool. Our Reader's Club page is already great, but I can also envision a Reader's Club wiki that allows libary users to instantaneously submit a book review of their latest and greatest reads. As with the Princeton example, wikis would also be useful for bookclubs and I can also imagine a virtual book club that meets and exists via a wiki and other online conference/communication tools.
I was also really impressed with the way the Library Success: A Best Practices Wiki was organized. I clicked on programming, then Programs for Young Adults and instantly had links to tons of great resources for Young Adult programming.