OpenBSD

Forked from the NetBSD project, and therefore sharing much of its history and portability, OpenBSD's hallmark is the priority given by its developers to careful auditing of system's code, which in turn contributes to the stability and security of that code. They also created OpenSSH. A more secure and open source alternative to SSH but compatible with SSH.

http://www.openbsd.org http://www.openssh.org