1. Set up several blogs on various niche subjects and write articles on regular basis. Add affiliate links to Amazon or Clickbank products, plus add Adsense to the blogs. You can earn via these and other channels. Or even create your own ebook or report or similar product.
2. Write ebooks and publish them on Amazon's Kindle Store. That's what I'm working on.
3. Learn copywriting skills. I recommend you take a look at www.awaionline.com . They offer a variety of home study courses. They are a well established and trusted company. I have been their member for a couple of years now and have purchased a couple of their products and they are excellent for any aspiring writer.
4. Sell your writing services on websites such as www.elance.com - you could offer to write articles, blog posts, webpage sales letters etc.
5. Open an online PLR store - write articles on niche subjects and sell packages.
Hope this helps a bit :-)