iPhone/iPod Touch users will know that while it is easy to sync music from iTunes to your iPod, it certainly does not work the other way round. It may be a great security feature by Apple, but it has definitely caused lot of inconvenience to its users. Luckily, there are lots of easy way to get this done.
The configuration of Senuti is easy and works out of the box. After installing, Senuti will prompt you where to save your music files and whether to add it to iTunes library. Once that is done, plug in your iPhone/iPod Touch and it will automatically detect all the songs/videos/playlist in your device. Click Transfer and the all the selected entries will be transferred to the computer.
In Linux, it is more troublesome to sync the iPhone/iPod Touch with the OS, nevertheless, it can still be done via this tutorial.