NetBSD Project has released version 4.0 of the NetBSD operating system.
NetBSD is a free, secure, and highly portable Unix-like Open Source operating system and runs on most platforms. Mostly, it proves popular in production and research environments, and it is user-supported.
NetBSD 4.0 supports version 3 of the Xen virtual machine monitor, Bluetooth, many new device drivers and embedded platforms based on ARM, PowerPC and MIPS CPUs. It also includes iSCSI target (server) code and an implementation of the Common Address Redundancy Protocol.
Security is also beefed up with restrictions of mprotect(2)
to enforce W^X policies, the Kernel Authorization framework, and improvements of the Veriexec file integrity subsystem, which can be used to harden the system against Trojan horses and virus attacks.
Currently, the software runs on 54 different system architectures featuring 17 machine architectures across 17 distinct CPU families, and is being ported to more.
It can be downloaded here