[rounz]

ill add another vote for dropbox, it can play the track direct via its flash interface (it does same with photos) if thats not sufficient then move it into your public folder and send them the url.. plus you get to see how good dropbox is, hell you could even up in its current wav format if you wanted, depending on its quality mp3 or ogg wouldnt halm it much and you might be able to improve it with filters/replaygain

megabannerupload.net ? in archives ? or posting a cd ?
heck of alot excess effort imo, no need