BowerStudios.com

my secret command:
exiftool -r '-FileName<CreateDate' -d %Y/%m/%Y%m%d_%H%M_%S_%f.%%e dirToSort

Creates files such as:
2009/02/20090201_2352_32_IMG0020.jpg

You can find it on Ubuntu in the libimage-exiftool-perl package:
sudo apt-get install libimage-exiftool-perl