Hello,
This is just an idea but here it goes :
I think it would be interresting if there were a way to add user-defined metadata for any given file in any given directory.
For starters, the metadata could simply be a text field ("annotation" or "comment") that the user could fill in for a given file through a context-dependent menu (right - click or whatever). Afterwards a user could search for keywords in annotations of all personnally annotated files.
Personnally I would fin use in such a feature. I could for instance right click on a openoffice document file (or a WAV or OGG for that matter) and place a comment on that document for further reference.
I think the annotations could be saved in a hidden file stored in the same directory as the annotated file somewhat like the .directory file is used for icon definitions in konqueror. Of course, some other type of indexation could be more appropriate (sqllite or something of the sort)
Cheers,
Fred.