Earlier this year, I started several podcasts for local public radio station KPBS-FM. In the process of getting them online, I modified a podcast button that was becoming popular . In terms of usability, I think average users are still behind the curve in understanding technology abbreviations like XML RSS etc, and opted to make it instead. The orange color is the only real standard at this point, and people do know what MP3s are. I posted that version of the button in April, and to my knowledge, it was the first podcast button to make this distinction.
So today, I noticed that Youth Radio is now podcasting, and guess what? They used my button!