From MakeTechEasier:
In Mac and Windows, you can easily sync your iPhone/iPod Touch with iTunes, but in Linux, there is no easy way to sync your iDevice’s music library with any of the media player. Even if you are willing to jailbreak your phone, there are still plenty of complicated steps that you need to do to get the syncing to work. With the release of iFuse (and a bunch of other library), things have changed. Not only can you mount your iPhone as an external drive in Ubuntu, you can also use it to sync your music library with Rhythmbox.
The following tutorial only works in Ubuntu Karmic (and other karmic-derivative distro) and iPhone firmware 3.0 and above.