Just spotted the your network option in del.icio.us. Nice idea, would like to do the same in Flickr. So heading over to the del.icio.us blog, I found a recent entry.
To make sharing easier, weve just released a new feature called your network. You can add other del.icio.us users to your network either by visiting their del.icio.us pages or from the your network page itself. Once someone is in your network, you can keep track of their latest saved public bookmarks. And when you save new bookmarks you can easily share them with people in your network just by clicking on their username.
In Flickr there is the ability to send pictures to a set of pictures but not to a group or person. Once you've uploaded it you can then send it to a group. But the nice thing about the delicious way, is that its using Tags instead of some other thing.