ffmpeg on Fedora
While building and installing ffmpeg on Fedora core 4, I ran into this problem. The standard installation with lame configured couldn't find the lame shared library. This is because lame puts the library in /usr/local/lib instead of /usr/lib where ffmpeg looks. Making a symlink fixes the problem.
ln -s /usr/local/lib/libmp3lame.so.0 /usr/lib/libmp3lame.so.0