Since we're on an OS design kick:
http://arrakis.cs.washington.edu/
From the sound of it, this is like a 64-bit, multitasking, multikernel, memory protected version of FreeDOS. I'm not sure if that's amazing or insane.
(NB, it's based on a Microsoft research OS called Barrelfish, which MS thankfully opened the source code for after abandoning. From when I last checked the sources, not a lot has yet been changed from Barrelfish.)