OpenSSH, LibreSSL, OpenIKED, OpenSMTPD (with spamd for greylisting) are great. The man pages and FAQ is really useful.
From their website:
The OpenBSD project produces a FREE, multi-platform 4.4BSD-based UNIX-like operating system. Our efforts emphasize portability, standardization, correctness, proactive security and integrated cryptography. As an example of the effect OpenBSD has, the popular OpenSSH software comes from OpenBSD.