Actually I think that is what a lot of systems are moving towards... a real-time outliner/wiki. I use WorkFlowy with others to manage releases and other informa

Actually I think that is what a lot of systems are moving towards... a real-time outliner/wiki. I use WorkFlowy with others to manage releases and other information and with just a couple multi-user oriented feature it would match your description. Trello is in this direction as well. Google Wave just felt toooo real-time and free-form.