If you're on a Windows PC, there is a new backup utility that claims to be able to backup your songs / media across to your PC. You can download it
here. Requires knowing your iPhone's IP address and root password - but installs only on Windows.
Please note - I have tested this app for things like Notes db and Summerboard themes etc. backup / restore - I have not tried out this media backup feature.
I've covered some general tips on using the program
here as well ...