The seL4 microkernel
seL4 is "The world's first operating-system kernel with an end-to-end proof of implementation correctness and security enforcement" originally developed (as far as I know) at UNSW, further developed at NICTA.The original project home page is at http://ssrg.nicta.com.au/projects/seL4/ and the new page is at http://sel4.systems/Downloads at http://ssrg.nicta.com.au/software/TS/seL4/