I think it plays DivX by default, at least the version that you download from the MPlayer homepage does. If not, you can download the win32 codecs
, and unpack the codecs to your win32 codec directory, usually /usr/local/lib/win32
. If that directory does not exist, then run mplayer from the command line and check the output, there should be a line that says something about "can't find win32 codecs in..." or soemthing like that. Put the codecs in that directory.