Swg.fm is probably one of the simplest ways to share your music amongst your twitter community. Simply enter an artist’s name, song, and your twitter name, and click send. Thankfully, the service doesn’t send the tweet for you. Instead it redirects you to your Twitter profile with the basic information for tweeting your song.
From there, customize the tweet however you’d like. Clicking on the provided link for your song will take you to another page that displays a video or mp3 of the song you’ve tweeted (if recognized). Thus far, it’s been completely accurate for me.