A few additional creative uses I'd thought about:
- I could see bookclubs or reading groups using the list functionality to keep track of what they've already read, and to solicit potential new titles from the members.
- For the academicians among us, you could load up the required readings from a syllabus into a WorldCat list--students could see at a glance which editions/articles were available at the library, what was checked out already, available as an eBook, etc.
- Maybe a family could track their library-movie-watching together, through a WorldCat list. Or a teen could post out the coolest sounds s/he has heard from the library's eclectic music collection...