I figured a thread dedicated to the most important safety item in an off-road vehicle was needed.
a few basics on building roll cages
you can use sch40 also known as poop-pipe but it is not recomended and you will die
I like to use either DOM or HREW structural tubing, it is designed to be structural not to carry fluid/liquids. I use 1-3/4" but it really depends on what dies are available for the bender you will be using.
I figured that I would post some pictures of the Toyota cage that I am building at work and some others to give some ideas of how to build a roll-cage that both looks nice and will protect you in a roll over.
Some designs will be very simple and other more elaborate but always remember triangulation is your best friend in roll cage construction.
here is my bender
http://i46.photobucket.com/albums/f1...2-03185258.jpg
and the begining of the Toyota cage the double B-pillars
http://i46.photobucket.com/albums/f1...3-16133700.jpg
http://i46.photobucket.com/albums/f1...3-16133643.jpg
oh and it fits in a standard cab truck