This program has the ability to dump to a WAV file with the command mplayer foo.wma -ao pcm. This will put a file called audiodump.wav in the current directory. Of course, this won't work with multiple inputs, so I whipped up a quick shell script which renames audiodump.wav to foo.wma.wav, then moves the original file to the trash, and then processes the next argument:
#!/bin/tcsh[Editor's note: I haven't tried this myself...]
while($#argv != 0)
mplayer "$argv[1]" -ao pcm
mv audiodump.wav "${argv[1]}.wav"
mv "${argv[1]}" ~/.Trash/
shift
end

