Some tracks in my music library only consist of introductory talk and things like that I usually want to skip. Is there a media player that can be taught to not play certain tracks, either using ID3 tags or a blacklist? I looked at Rhythmbox, Banshee and Quod Libet but so far didn't discover a built-in feature or extension like that.
You can use gmusicbrowser for that. It includes powerful filtering options which allow you to add filters (or intelligent playlists, as other players call it) such as "Comment does not include '[SKIP]'", "Rating >= 50%" or "Rating set to default".
When creating your filter rule, be aware that comments are saved in the file metadata while ratings are saved in gmusicbrowser's settings file ;)