Misu

Misu is for people who want to discover a whole new world of music. Just connect two or more iPods to your Mac, and watch as Misu fuses their music libraries into one.

And Misu is smart; only the songs that the receiving iPod doesn't have already will be copied. The slick interface lets you do all of this with ease and pleasure. Try Misu today, and get a taste of what the Mac is missing.
Misu works with all iPods, including the iPod Touch and iPhone.