drag and drop from library

i recently discovered that you can drag and drop object instances directly from the outliner to the scene. but is it possible to have objects in the outliner which are not in the scene, so that i can use the outliner as a library from which i drag my objects in my scene?

similiar to what he has in the video at 1:03, which is in cry engine 3.
http://www.youtube.com/watch?v=eeKS9P7XDf4

Create a new scene and put all your objects in that scene. You can still then drag them from the outliner into your working scene. These would all be in the same blend file. You can have them in an external blend and just append or link them into your current blend (not drag & drop)