Do you know any teens of young adults that love to write, especially fiction? Then you must tell them about the website Figment, "a community where you can share your writing, connect with other readers, and discover new stories and authors."
It is very easy and free to sign up for Figment. Once in, members can write almost anything from short stories to fan fiction to poetry. It is completely up to the writer to decide whether to make their finished product public. If so, it goes into the Figment library, where other members can read, rate and comment on it. There are many guidelines in place dealing with respect of others.