If you read the following and ask, "why?" then just stop reading :-)
This is a great hack for Mac OS that uses Skype, iTunes, and a POP3 mail account to play any song in your iTunes library on your cellphone. Send an email from your phone to the configured mailbox, the script checks the message for keywords, passes them to iTunes, creates a playlist, uses Skype to dial your cell, and routes the audio to you over the phone. Sound quality is horrible but, well, that's not the point.