I have noticed that there are many projects that reproduce the same sample conversion routines for changing sample rate / frequency / endieness / channels. Of the top of my head: esd/arts/xmms/madplay/ libaudiofile.
Perhaps there is already such a library, but if not I was hoping that this could warrant the creation of a second 'companion' library to mad (libresample or something). It could also contain down mixing routines for combining channels.
just a thought
sam