I have been using All2MP3 for Mac for years, not much it won't convert to mp3.
NOTE INFO AT THE BOTTOM, NO LONGER SUPPORTED.
All2MP3 is a free application for Mac computers, with a simplistic interface, designed to do one thing: convert your audio files into MP3 files. It doesn't require a help file -- All2MP3 is ready to use from the moment you launch the app, but we did find that it wouldn't convert all file types.
The application's interface is as simple as its installation: just a simple drag-and-drop window, and an Add button that can be used to browse files. All2MP3 supports a wide variety of audio formats, such as MPC, APE, WV, Flac, OGG, WMA, AIFF, WAV, and even video formats such as Apple's native MOV format. It excels at what it is supposed to do, and during our testing we loved the speed at which it converted our movie and audio files to MP3. You can use a slider to adjust the quality of the final MP3 file from "Less" to "Super," as well as change the path to where the file is saved. We were pleasantly surprised when we looked at the timer after putting the application to work to convert a huge number of audio files. We were also surprised by the audio quality after converting MOV video files.
The one downside we found was that All2MP3 couldn't convert iTunes' M4A format, but with its performance on other file types, we still feel this is a very handy addition to your Mac toolbox. Overall, All2MP3 is a useful little app that fits the bill if you are looking to convert most files into MP3 quickly and for free. Its simple interface makes it ideal for all levels of users.