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 a pen name and did exactly this. She ended up being approached by the head writer of the tv show she was basing her fan fiction on and given a job based on the responses she'd received from the fan site.
You could even create a fan fiction thread about one of your own books or series and continue writing in the forums to drum up interest in your books. There is a wide variety of 'worlds' which exist in these fan fiction sites and no limit to where you can take characters.
Something for every writer with the time to market themselves to think about.
http://www.fanfiction.net/ is a great example of this.