* Plan9port (Plan 9 from User Space) ports a number of the Plan9 programs to Linux: http://swtch.com/plan9port/
* wmii (http://en.wikipedia.org/wiki/Wmii) is a tiling window manager that allows configuration through a Plan9-like filesystem. A number of people I know (myself included) were first introduced to the power of Plan 9 through wmii's extensive configurability.
* Go (the language) has borrowed a number of elements from Plan 9. One of the two main compilers (gc) traces its origin in the plan9 toolchain.
* Acme/Wily (the text editor). I'll have to confess that I never took to this much (as a Vim user), but give it a shot.
It seems to be distributed. If you are running Plan 9 on 3 machines, and one goes down, what happens to the rest of the system. Does it become unavailable?