in your documents folder open the itunes folder, in there is a file named itunes music library. If you just want to let your mac friend know what music you have you can send him this library via some ftp.
to give mp3s to your pc friend just use some ftp tool like hotline or websharing....then they can dl anything off your computer.
edit; your question is confusing though so dont know if that helps
[ 08-08-2001: Message edited by: el chupacabra ]