Robert Watson wrote on the FreeBSD Stable mailing list that FreeBSD 8 now supports Apple’s Grand Central Dispatch:

…may be interested in using Apple’s GCD technology on FreeBSD. GCD, for those who may have missed it, is a concurrent programming framework introdued in Mac OS X Snow Leopard, now also supported on FreeBSD.

There are a number of useful links on the wiki page, but this provides the best high-level introduction.

Read the post here

FreeBSD GCD Wiki page