NixOS 16.09 “Flounder” has been released, the sixth stable release branch. See the release notes for details. You can get NixOS 16.09 ISOs and VirtualBox appliances from the download page. For information on how to upgrade from older release branches to 16.09, check out the manual section on upgrading.
NixOS 16.09 released
Mon Oct 03 2016 announcements