PhoneTrans

With PhoneTrans you can manage the content of your iPhone or iPad more freely than you can with iTunes, as it permits you to manually add music.

You can also export content from your device directly to your hard drive, in case you'd like to make a backup copy of your music or applications onto a computer that doesn't contain your personal iTunes library.

Its interface is similar to iTunes, allowing you to navigate through your device's content, which is divided into Music, Video, Applications, Books, etc. There are buttons at the top of the screen to import, export, and erase content.

This is without a doubt the simplest and least-restrictive way to manage your iPhone, iPad, or iPod Touch content without having to deal with syncing through iTunes or risk losing your content because of errors or inconsistencies in your library.