So there's been a lot of talk over the years of what makes up a real GNU system. In 1991 the Linux kernel came along and, being under the GPL, the GNU project decided to use it because they had all of the rest of their components - all they needed was a kernel. Development on a kernel was already underway, however, on a kernel directly from the GNU project. They came up with a microkernel called GNU Mach and then a set of low-level servers on top of it that they called GNU Hurd.
Today the Hurd is still under development but it's come a long way. The one distribution that's alive and kickin' is Debian GNU/Hurd. It's a great challenge to get up and running because you have to use another Unix/Linux system to format the partition with special settings and then configure GRUB manually. Oh yeah, it doesn't come with a /dev/random, which you need for SSH to work.
I've already deployed a virtual machine with it and after a bit of compiling and Googling I managed to get an Apache/PHP/MySQL server running on there. It was pretty cool. Except the VM took literally 10 seconds to serve a page (I clocked the page generation time). I just freed up a hard disk so I'm giving this a try. Thought all you hardcore Linux geeks might enjoy hacking away at this thing a little.