Ubuntu :: File Manager Than Can Organize By Tags - Like An Image Manage?

Over the years of working with both images (many) and other files (many more) it seems that it is easier to organize images. There are a variety of image software (digikam, gthumb, the new "shotwell") etc. Its easy to organize them with multiple references - date, multiple categories etc. This in fact makes it easy & efficient in our multi disciplinary world to access the same image for multiple needs.

However the same is not true for other files (od formats, pdfs etc etc) the only way we seem to be able to sort them is by what folders we make. Of course we can use meta search engines to find it by other keyword / dates etc. But it is not the same as being able to give multiple tags to a file and later being able to retrieve by that particular tag.So am wondering if such a file tagging / sorting and accessing "thingy" already exists and if so what is it. Or it is available and i don't know where to look.