I'm the author of TMSU. If you've not heard of it before it's my pet project that lets you tag your files (from the command line) and then mount a virtual filesystem that lets you access them, by tag, from any other program, including those with graphical interfaces.

I've just released version 0.5.0, which has a number of new features and bug fixes. This version also provides a Windows binary for the first time, though it's a bit buggy at the moment and doesn't include a virtual filesystem (I'm working on that).

Usage goes something like this:

    $ tmsu tag photo.jpg holiday country=spain year=2014 family
    $ tmsu tag song.mp3 music big-jazz good
    $ tmsu files music
    song.mp3
    $ tmsu files "year > 2010 and holiday"
    photo.jpg

    $ mkdir mp
    $ tmsu mount mp
    $ ls mp/tags
    big-jazz  country  family  good  holiday  music  year

• Homepage: http://tmsu.org/

• Project: https:/github.com/oniony/TMSU/

• Download: https:/github.com/oniony/TMSU/releases/0.5.0