I do have a blog dedicated to writing (Writer Worries), as well as a blog for my book series (The Homemaker Helper Series). In addition to my blogs I write here on Hubpages, Triond (this one has been a little frustrating at times, but they have a lower payment threshold which is nice), Helium (I am earning a few pennies a week on this one, but also haven't submitted much on it lately), Ezine Articles and a few others. I signed up to several just to test the waters and see where the most income would come from. So far I have to say HubPages is the one that provides the most passive income.
I just read a book on marketing e-books and the advice was to spread the word and sign up to several sites; it is much the same for articles in my opinion. The more exposure a person has, the better chance of earning from it.