You could upload any mp3s you wanted, get Muxtape to host a mix tape for you, pass the link around, provide download access to the MP3s etc.
While Muxtape is set to make a return and allow the hosting of playlists again, there is an opensource alternative in the form of Opentape. It’s been around for a while but it was only last night I got to roll out a self-hosted version for the Playlist Mix.
It is opensource so it will be as flexible as you decide to make it as this custom design shows.
The idea is simple – upload it to a folder on your server (you need to be running PHP5+), set an admin password and start uploading your tracks. There doesn’t seem to be any way at present to make multiple mix tapes from one install though there’s nothing to stop you rolling out the script into multiple folders. You can then upload tracks through the browser interface or ftp them into your songs folder and away you go.