I often get questions related to how I store my digital images on my hard drive, and why I do it the way that I do it. Keep in mind that this is my system, and not necessarily something that will work for other people. In the absensce of database driven applications such as Aperture or Lightroom, using a physical file structure has been a necessity for me.
First off, my folder structure:
_Photos\year\yymmdd 'job'\filename.xxx
All of my digital photos are stored underneath a folder called '_Photos'. I put an underline before the word Photos because it will sort to the top if there are other folders near it. After that I have all of my photos separated into different folders by year (4 digits, such as 2004, 2005 or 2006). Then I have a folder for each day or each job in a given day (if I happen to have more than 1 job or separate shoot in that day, they will be separated). For example: '06.22.02 Serengeti'. If this folder somehow gets separated from my '2006' folder, I know where it should go. I guess I could put in MMDDYY format, but this is how I started off organizing my images way back in 1999 with my first digital camera.
Then my file naming logic:
yymmdd_hhmmss_job_imagenumber.xxx
So, the year at the front of the filename, then the hours, minutes and seconds, then the job name, and then a 3-digit image number for that day, starting with 001. Why do I put the hours, minutes and seconds into the file? Simple. I often shoot with more than 1 camera, and this allows me to have all of my images in chronological order, even if I am sorting by filename in either OSX or Windows XP.I do have separate folders called 'Portfolio - Africa' and 'Portfolio - Africa Misc' that I place all of my converted raw files into. These are mostly layered Photoshop files in 16 bit, converted by whatever raw conversion application I was using at the time. This approach is going away, as I adopt a more database-driven approach, where it is not necessary to always export an image to be worked on in Photoshop.Well, there you have it. A simple, well defined structure on my hard drive for all of my images.

"Which Way?", Cape of Good Hope, Africa, April 2006
Canon EOS 5D + 24-105mm f/4 L IS