Xinestarter is a small utility to preview video and music files of the selected target directory. It can also handle subtitles.
Do not forget to execute it in console (at least once), to see the available options.
-Kaffeine Player (>= 0.8.2)
(for the KPart to embed as the preview window);
Tarball contains sources and binary.
Hope you enjoy it. I'm addicted to it since 2005 :-)