Aperture & libraries
You can export folder (in your example 2009) as a library. This self contained library can be stored where you like and once reattached it is very easy to switch libraries from within Aperture. The only shortcoming of this is that images from 2009 are only available when that library is open.
|Demolition by Dutch Newchurch|
from Your City - Demolition
|Beautiful Kyoto's girl in Kimono by Fuji san|
from Miss Japan
|All pink by Minas_Eye|
|Jaguar Hood Ornament by edandgini|
from J is for ...