I looked into web albums a while ago, though I wasn't looking for multi-user functionality, since it's just me. None of the open-source apps really struck me as the bees knees. I had a very strong dislike for the presentation on Gallery, though. I ended up doing my own album with emAlbum, but I had to do a bit of hacking at it to make it a bit more palatable (I'm still not totally thrilled with it, but momentum keeps me from changing it to something else). Looking at the features, though, emAlbum doesn't appear to have multi-user support.