Teens Only

FictionPress :

[ Teens/Mature Teens ] - A showcase of fiction writing and poetry, post up to fifteen writing pieces to be read and published on the web.
Merlyn's Pen :

[ Teens/Mature Teens ] - Features a searchable library of teen-authored works which can be read online at no charge.
Noble Online :

[ Teens ] - Explores the writing process and provides opportunities to fine tune skills. Students may write on weekly topics, submit their work for publishing on the site, and receive feedback.
Pomegranate Words Writing Contests :

[ Teens/Mature Teens ] - Offers free monthly contests for poetry and fiction for teens 19 years old and under.
The Squid :

[ Teens/Mature Teens ] - An online magazine publishing the stories of young writers, with submission guidelines and author interviews.
TeenLit.com :

[ Teens/Mature Teens ] - Publishing original compositions and book reviews, with discussions, contests, workshops, and links to author home pages.
Write Stuff Club :

[ Teens/Mature Teens ] - Club for amateur young writers, from the age of 13 to 23, including a postboard, a regular newsletter, pen pals, writing articles, and the chance to be published online.
The Young Writers Club :

[ Teens/Mature Teens ] - A online postboard community for teens to get feedback on their writing and talk about writing in general.
Young Writers Society :

[ Mature Teens ] - Provides forums, newsletter, ezine, contests, blogs, a chat, and online resources for people aged from 13 to 25.
Zeen :

[ Teens/Mature Teens ] - Accepts submissions from teens around the world. Publishes stories, articles, poems, and editorials.