Organize by year, then type, the specific item. (Score 1)

This has been working well for me for approximately 8 years or so:

http://boykin.acis.ufl.edu/~boykin/2005/projects/directory_policy/policy.html

The main benefit of organizing by year is that once the year is gone, you know that directory will never be written to again, so backing up becomes so easy, I actually very regularly do it. A little rsync, a few computers, and periodic DVD burning means I haven't lost any data in a long time.