I don't quite know what to use for terminology, so bear with me...
Are there any cross-platform frameworks out there that facilitate a kind of "virtual file storage" to encapsulate adding files along with a database of metadata? I'm thinking about something along the lines of iTunes or iPhoto, where the program manages a whole bunch of files (in those cases audio or image files) and has a database of metadata so you can organize/find those files easily. I'd like to cobble together something along those lines for files in general.
edit: I am hesitant to store files in a database alone, e.g. MySQL, as there would be potentially tens of gigabytes in my application (this issue has been mentioned in several SO posts, see this one that gives several links to others). I'm looking at CouchDB though and maybe it has promise....