Let me go ahead and say it: I LOVE WIKIPEDIA!!
I know, I know--Wikipedia should never be a cited source in an academic paper, nor should it be the first place you turn if you are looking for authoritative information on a given subject.
However, the wonderful thing about Wikipedia (and wikis in general) is that the information is written by people who are passionate about their subject. Everything on Wikipedia is researched, written, and organized by people who simply want to share what they know with others. I find that amazing. Taken with the requisite grain of salt, Wikipedia can be a goldmine of information on every subject you can think of (and tons you can't.) Anything you want to know is a click away--history, pop culture, science, literature. Even better, many keywords are hyperlinked, so you can literally follow those threads along the site for hours.
Done gushing about Wikipedia now, I promise.
I found all the wikis listed under the discovery exercise to be wonderful as well. I'd love it if our library could have something like SJCPL's subject guides, which is almost like a FAQ in the amount of ground it covers. It strikes me as a wonderful way for customers to get their questions answered, with helpful links for them to follow as well. I also liked the booklover's wiki. Having something like this would be a great way for customers to interact with us and each other, as well as create browsing lists of titles for them to look through--after all, how many customers wish we had something like that for DVDs? This would be a great start.