I wanted to have entries which I printed from my bibliographic data base flagged. That is, being able to know if I already have a hard copy of an article for example.
In BibDesk preferences » Fields I added a boolean field called 'Printed.' Then I created a smart folder which contains all the entries with this flag true.
The non-computerized part is having a physical folder where I store alphabetically all the articles I printed. This way I can easily find papers without re-printing them.
[crarko adds: I haven't tested this one. I admit I had never heard of BibDesk before, so if others have need to manage a bibliography and haven't tried it, here is something new for you, too.]

