No Windows, você pode usar iDump para extrair músicas do iPod e depois jogá-las no iTunes.
This program will allow you transfer your songs from your iPod to a PC, iDump does come wrapped in installer but you can simply drop the .exe in the root directory on your iPod and run it from there.
No OS X, há expod :
expod is a small utility for getting songs off your iPod. iTunes does a fantastic job of copying music onto an iPod, but lacks the ability to go the other way. With expod you can copy any or all of your songs (or videos) off your iPod, using whatever file naming convention you like.
… e podUp , ambos gratuitos também:
podUp is an application which copies all your music files from your iPod to a folder of your choosing, without having anything to do with iTunes.