Where can a writer get the best bang for their FREE buck in marketing themselves?

Looking for a free option for marketing yourself as a writer? The best idea I've heard of with actual results  is joining a fan fiction site or two. You pick your favorite (or most popular) tv show or book series and start writing fiction based on those characters.

There are literally thousands of ready made fans at your fingertips salivating to read something fresh based on the characters and world(s) they've grown to love.

A friend of mine who is an accomplished writer went under...