Converting m4a to mp3

Have discovered an easy way to convert m4a to mp3. I already have dwhelper installed on Firefox on the Mac, so after making a voice memo on the iphone, I email it to a blog account that will host it (I used Posterous.com in this case) and used dwhelper to download it as an mp3. Great stuff!
http://liliansoon.posterous.com/lia-singing-in-french-0