I see on this other question (Group sharing photos without registration) that there are ways to do this without registered accounts, but I want to do the same with registered users (ala a family account). I want my users to be able to create albums, add photos to each others' albums, all while keeping the photos private within the family, until otherwise specified.
Given that all of my photos are already in Picasa locally, I'd like something compatible with Picasa, but I'm open to other solutions as well.