has step by step instructions on how to build and start a jail. Search on google also there is some nice wiki's out there about jail8 and there is some other good links i got at home but you will have to wait for a few hours after i get home from my DC to post them
Various patches and some docs on Jail8 for FreeBSD. (Note I am having problems accessing this site right now) http://garage.freebsd.pl/
And ofcourse the good ole FreeBSD handbook has more docs and the man 8 jail is a great start. Also please note that there was a SA released against jail 8 on the 5.x platform. Please be sure that you are fully patched up.