Just experimenting with http://twaud.io for tweeting music files of up to 10Mb.
http://twt.fm offers you the ability to re-use your files uploaded from other places, such as libsyn, youtube or soundcloud.
http://twiturm.com offers you the ability to upload a whole track and creates an RSS feed, but without podcast enclosures.
http://twaud.io offers you full podcast enclosures, so you can plug the feed straight into iTunes, but 10Mb is limiting for music podcasters. Would be great for those submitting audio for NaPodPoMo this year though!
Also seems a better option for non-Iphone users than http://audioboo.fm.