I like this SoundCloud one the most, mainly because I have found sound clips on it before. So I was already familiar with the website, but not the app. I think this would be a great idea for a program. Get patrons to come in and make their own radio programs complete with voice overs, hand created sound effects, etc.
Granted this would take several hours to complete something, and probably more realistically several programs to get something into the final stages. However, it would be a pretty rewarding.
Or you could even record yourself reading a book for story time. I remember that when I was a kid I would dial into the one that the International Falls library did. Or even read a book, and send it to your grandkids who live on the other side of the country. The wonders of the spoken word!