I've shared my Poetry online for a few years now. I started off posting them on a couple of official sites where they are copyrighted to my name, now I just put my copyright on them...{©2008 Jan B....} (Full name in some places!).
It doesn't always make them safe from copying/stealing...but there's nothing you can do really...all I know is...I haven't found anything of mine copied/stolen yet online! lol