The Lethe Kernel
Unlike most operating system projects, I'm not extremely interested in the kernel. Gesturing vaguely at the development histories of various major microkernel platforms (Darwin, MINIX, Hurd, QNX, L4...) there's some evidence that purism doesn't scale well in concert with a POSIX API.
The good news is that Lethe isn't going to be POSIX-compliant. It is meant to be cruft-free.
More on this as it develops.