-------------------------------------------------------------------
wget http://downloads.xiph.org/releases/theora/libtheora-1.0alpha3.tar.gz
tar zxvf libtheora-1.0alpha3.tar.gz
cd libtheora-1.0alpha3
./configure && make install
cd to Mplayer source directory
./configure && make install
--------------------------------------------------------------------
on OSX, WinXP? and (of course) our all-favourite leenux, vlc (aka VideoLanClient?) plays ogg/theora streams fine. hxplay (helixplayer) should also work.