MuVOn is a Linux-based application for managing files and playlists on (originally Creative MuVo) mp3 players but can copy files to just about anywhere.
mp3manage lets you organize your mp3 and other music files the way YOU want it. This includes renaming and tagging them, creating playlists and sorting them into your music directory.
GUIPod is a KDE/Qt frontend for managing the Apple iPod(TM) from a
firewire enabled Linux machine. GUIPod uses GNUPod tools as its backend and provides song management features such as playlists, song sampling, tagging of songs etc.