<p>Greetings,</p>

<p>I'm trying to find either a free .NET library or a command-line executable that lets me convert M4A files to either MP3s or WMA files.  Please help :).</p>

Found it!
http://pieter.wigleven.com/it/archives/3
There may be other solutions, but this is gold for what I was looking for.
P.S. I've written
a .NET DLL
which handles this behind-the-scenes. It's pretty terrible code, but it gets the job done.