I definitely don't have a perfect system, but this is what I have done with some success: I have my clippings, magazine articles, etc. organized by theme/subject: such as "animals", "flowers", etc (organized alphabetically).--I have a section for "Artists", in which I put articles about specific artists. These are all in a regular filing cabinet. I put larger reference materials (larger visuals, etc.) in posterboard folders, stored flat in a drawer. These are labelled with themes like "Impressionism", etc. I teach elementary art also--and I have found this works better than organizing by grade level. Having all these in a data base, so I could find them would be great--cross-referenced, etc.--but who has time to do that? If I could find a parent helper who would really like to get into it...........
In one of the magazines--Arts & Activites, I believe--Guy Hubbard, who writes many art history related articles, advertises his system for organizing reference materials. At least he used to--he gave an address where you could write him, and he would send you an article describing his method. I sent in for it, and it looked interesting--but I haven't pursued it further.
I'm interested in hearing the feeedback about this issue.