Ask HN: List creation and sharing

Hey HN. Do any of you remember what Path was rumored to have been doing before the whole photo-sharing thing?

http://www.readwriteweb.com/archives/first_peek_at_pathio_the_stealth_startup_from_face.php

It was supposedly something along the lines of list creation. Now, I don't know about the rest of you, but I was actually SUPER excited about this, because I really wanted an app that I could use to make, share, and collaborate on LISTS. Seems trivial, but I thought it was awesome.

Even now I can't seem to let it go. So I'm asking you HNers, do you know of any apps that do this really well? I'm not talking about todo-list apps, I know tons of though. I'm talking about a single unified interface that allows me to easily and quickly create lists (of any kind, with any sort of content), and be able to share them live with friends, and allow friends to edit them.