I found a website called List Dump (maybe its just one word?) at www.listdump.com
It was pretty neat, I make a lot of lists myself, and constantly have those "top 5" discussions with my friends. I think it could be useful for a library. People could create themed lists, say All Time Greatest Books on the Circus. THen people could add to the lists the books they believe should be on there. And then everyone who wanted to had access to these lists, and they could find out about all sorts of favorite books on the circus. I can also see this being useful for coordinators. They may keep up with the lists and if they find that the library does not carry a popular item then they may choose to order it, and they could post into the list that this item is now on order upon finding out about it via this list.