Amarok: Amarok is a powerful music player for Linux and Unix, MacOS X and Windows with an intuitive interface. It makes playing the music you love and discovering new music easier than ever before - and it looks good doing it! Amarok has integrated Last.FM, Magnatune, Ampache, MP3Tunes, Jamendo, OPML Podcast Directory and Librivox as well as support for your Apple media device via plugin.
Rhythmbox: Rhythmbox is another music management application inspired by iTunes. It's goal is to offer users all the functionality of iTunes on the Linux platform. Rhythmbox is designed to work best under the GNOME desktop environment but can also be run on KDE with the installation of a few GNOME dependencies.
Exaile: Exaile is a music player and music manager designed in python for the GNOME desktop. It was inspired by the popular KDE music management application, Amarok. It aims to give you all the same options as Amarok only written specifically for the GNOME desktop. It offers many of the best features of Amarok, including Album art fetching, Last.FM scrobbling, support for large libraries, a shoutcast directory, an advanced tag editor and iPod support.
Banshee: Banshee is my personal favorite iTunes replacement. It has all the options I need to manage and sync my iPod while still offering podcasts, internet radio, last.fm scrobbling and audiobooks. Banshee will also play all your videos and sync with your Android device should you own an Android smartphone alongside your Apple media player.