GoboLinux is a GNU/Linux distribution which radically changes the directory structure, leaving FHS in the dust.
It's mainly a curiosity, but it works and proposes an interesting way of handling packaging for domain specific package managers withing distribution package managment systems. To understand that last sentence think about how Debian packages CPAN, gem, LuaRocks? etc...
One page links to GoboLinux:
http://www.gobolinux.org/