If you're running Mac OS X, you now have another way to copy music, videos and photos from an iPhone back to your computer with ease. iPhoneDrive is a tool that was initially created for storing files on the iPhone as if it were a removable drive, much like the iPod's disk mode function (which is missing, by default, from the iPhone). The new release, version 1.2, allows you to copy files that are stored as music, photos and video on the iPhone (synced from iTunes) back to a desktop Mac.
This feature allows you to, for instance, sync music from one Mac or Windows PC to an iPhone using iTunes, then extract the same music to another Mac.
PodWorks is another utility that can accomplish the same function. As previously noted, when used in conjunction with SwapTunes, these tools are effective means for moving music from one Mac to another while retaining a base library on your iPhone.