I've added the ability to pick on different entities in the resource browser and they'll show up in the little preview window. They can also be spawned into the scene as well. So you can now create new scene nodes and bring in new entities into the scene. It's coming along.
Notifications about object creation are all broadcast through an event system so plugins can hook in to this. I've got 5 plugins on the go right now: Basic Gizmos (translation, scale, rotate), Properties (shows the properties of the currently selected objects.. only scene nodes for now), Resource Browser (shows all movable objects, materials, etc and allows you to preview entities), Scene Node which shows you a tree view of the scene graph (nodes and movable objects), and a Test Plugin which is used to create the simple startup scene (2 ogre heads).
I will work on deleting objects soon and then figure out a way to do renames. I then want to move on to looking into Undo/Redo actions. It's getting there. I want to do some more work on the game as well but my life has been kind of up in the air for a while.