You can try getting a foot into the freelance market...my favorite site is Elance, though I've also used Guru with some good results. It does take a lot of work to get to the point where you're consistently getting new work, and nearly all of the jobs you're going to get will be for full rights to what you've written, but you write a set amount for a set payment that gets paid as soon as you're done. I am a full-time writer and do a combination of freelancing and affiliate sites/programs. The freelancing gets my set paycheck in, then my writing here and on Helium, Associated Content, and Epinions as well as my AdSense and other affiliate ads on my own sites is my recurring revenue.
At first the recurring bit may hardly seem worth it, but I strongly recommend setting a little time aside for it every day, eventually it will become substantial and it will give you a bit of the stability that freelancing is otherwise lacking. Right now I know that if something happens and I can't write anything new all month, I'll still get about 30% of my normal monthly income through recurring sources. In addition, you might just be surprised who finds your work on these affiliate sites...I have a few very steady and fairly lucrative clients that contacted me after reading some of my articles and seeing in my bio that I'm full-time.
As for Bhart's recommendation...I believe you'll find something if you search "Triond." I personally haven't tried it, but have heard good things. I've also had a lot of people recommend Suite 101 and Demand Studios, though again haven't personally tried them yet.