Okay, this will make me sound like fanboyism (I guess it is, but I am an Arch user - with our company running their servers on FreeBSD), but you might also like:
All of them are used in production, search engines (at least FreeBSD (Google backends and DuckDuckGo) and DragonFly BSD), space crafts (at least NetBSD (ISS)), internet service providers (all of them), resarch agencies (all of them), US government/military (well, I am not sure about DragonFly BSD in this case).
* http://www.slackware.com/
* http://www.freebsd.org/
* http://www.netbsd.org/
* http://www.openbsd.org/
* http://www.dragonflybsd.org/
All of them are used in production, search engines (at least FreeBSD (Google backends and DuckDuckGo) and DragonFly BSD), space crafts (at least NetBSD (ISS)), internet service providers (all of them), resarch agencies (all of them), US government/military (well, I am not sure about DragonFly BSD in this case).