The number of FreeBSD related operating systems is fortunately not as as high as the number of Linux distributions.
Most of you, if not all, will agree there are no FreeBSD distributions/distro’s due to the fact that FreeBSD is developed as a coherent operating system with a kernel and userland applications.
Existing FreeBSD based operating systems use the FreeBSD base and specialise in a certain field, e.g. DesktopBSD & PC-BSD concentrate on desktop use, pfSense and m0n0wall on routing/firewalling, AskoziaPBX on PBX systems etc etc. For more examples, check out this page.
Since these systems aren’t distro’s what would you call them? Please let me know on the poll below.