In Matt's official ToDo list 'Custom user lists' is listed. I imagine this will take care of this need. This is one of the improvements I am looking forward to. Ideally for me, I would like to separate as follows:
1. Collection
a. Hardware
b. Accessories
c. Physical Games
d. Digital Games (Steam, PSN, OnLive, etc)
I'm holding off of adding anything else because I like that my collection only has my physical games currently (plus a few hardware/game bundles).