Featured on Mashable: http://mashable.com/2010/07/26/how-to-audio-twitter/
As well as offering a paid-for service where “celebrities” will record a message for you to tweet, ShoutoMatic also offers the infinitely more useful and free service of letting you record your own tweets.
Head on over to the site, either sign up for an account, or connect via Facebook, and you’re ready to start “shouting,” as it were.
On the simple interface you just hit to record, review and save the clip. If you’ve signed in with Facebook it will prompt you to post it on there, but you can skip this bit.
After you’ve saved it, you can e-mail, download, post to Facebook or tweet your audio. If you tweet it, then Shoutomatic makes you a neat shortened URL (like http://bit.ly/ckvllv) and adds the text “Check this out” to your tweet, which obviously, you can choose to delete.
There is no listen counter on ShoutoMatic, but people are able to reply directly on your message page. Here’s what anyone following the link to your message will see: