Recs.
Updated
Cantata is a (yet another!) client for the music player daemon (MPD). Originally started as a fork of QtMPC, the code is now very different. Cantata can be compiled with KDE support, or as a pure Qt application. The interface is very configurable - most views can be shown as either a list or tree structure.
Specs
Pros
Pro Full-featured
Not only can it help manage a music collection but Cantata also features easily configurable dynamic playlists and support for a variety of audio-streaming sites and digital devices. Furthermore, it supports last.fm scrobbling out of the box (not common with mpd front-ends).
Pro Excellent at tagging/renaming files
Cantata can guess tags from what's already in your music directories and it can rename files so to match tag info (if that's what you want).
Pro Easy copy to mobile
The user simply needs to right-click in order to copy an album to their phone.