Suggest a site I'm familiar with, as below:
It's a safe and clean site, where writers of all sorts share their work.
You post yours (poem, chapters, short stories, haikus, and on like that; people add pictures, music... all kinds of things) and it will be reviewed by other writers...
especially if you start right in with reading some of the actually fine work to be found there.
Whenever you review someone else's work, they receive that review with an invitation to review your work, and so things keep going around.
It's a good site.
There are frequent contests as well in various categories.
I would avoid any ads re: self-publication though, as I believe them to be cul-de-sacs.
If it doesn't work for you, I'm sure you'll get other suggestions. Oh, and registration and everything is free there.
ADD: Just FYI, this site has people on it who are from everywhere, too.
2nd ADD: No one can steal your ideas. As soon as you write them and have a copy, (plus the site makes guarantees, and your 'name' is on everything you write), but even without that... your work is already yours, legally, in every way.
And I'm sure you know the definition of fanfic.