Plan 9 is an interesting Operating System, created in Bell Lab. Essentially by people that created UNIX.
In my opinion Plan 9 is an interesting operating system. Because it is unix in extreme form. Where everything thing is a file. Meaning everything including the network interface. Like unix it means that, there is consistent way to access an OS resource. Don't expect it to function like one. And don't expect it to look nice. What really interesting of plan 9 is the internal and the design.
Previously you can either install Plan 9 natively on machine, or use qemu to run it. Which is not hard. But now somebody have ported Plan 9 to vx32, sandboxing library. Which is something like vmware. And is very interesting piece of software, but that is for another post.
Currently it runs on *nix, which include os x, linux and bsd. Go to the links.Download it. To run it, in directory, you unzipped. in terminal type. ./9vx.Linux if you use linux. ./9vx.FreeBSD for bsd ./9vx.OSX for os x And Have fun then!!!!!