If you added MP3 support to the server... it'd be a good option I'd think. As it is now, the user must download the file in order to listen to it.
I'm not up on all of the methods to add MP3 support to a linux server... I just know it can be done since my own personal server has it rolled into it...
This should open a new window to a song made by a friend of mine that I did the mix down for... he never finished adding a lead to it before he passed away... but it's still a cool song.
Darkness into Day
Other options is to host the MP3's on a site such as Soundcloud ... I'm uncertain if there are limitations to the free hosting they provide or not... so that would need looked into as well. In addition, you can add Soundcloud support to the server so it'd actually act as if it were playing from your server even though it's hosted on theirs.
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Hmmm....
You may want to try to ftp the MP3 up to the site and then try linking to it instead... I see that file is listed as an attachment so may be why it's forcing a download instead of just playing it.