I would like to recommend Zoetrope: All-Story as a good place to begin if you want to submit a story. They consider unsolicited submissions of short stories and one-act plays no longer than 7,000 words. Do not submit storys between September 1 and December 31. Send stories to:
Zoetrope: All-Story
Attn: Fiction Editor
916 Kearny St.
San Francisco, CA 94133

Good luck to you, and happy writing.