Getting Shared Music Itunes

How can I share music without overwriting their music on iTunes? and Vise Versa?
So I want to share my iTunes music with my friends, but when I put their iPod in my computer, it says if I want to erase their music to add in my music. I also want my friends music, but it also says the same thing. So how can I share music on iTunes? Also, does it work with an iPhone?
Best answer gets 10 points.
You can share music with other iTunes users who are on your network or via Wifi if you go to iTunes preferences>sharing>share selected playlists. Also tell iTunes to look for shared playlists.
To share iPod music with another computer
http://www.howtodothings.com/computers-internet/how-to-share-ipod-music-with-another-computer
Shirley Bassey – GET THE PARTY STARTED – Music Video