Well established article directories are a great way to increase targeted traffic and gain higher quality inbound links to your website. Google rates some of them highly with Page Ranks of 5 or 6.
You can use pages of your website for the basis of any articles you write, I have seen exact copies submitted and accepted to article directories.
If you regularly submit articles to a directory around one core subject (your website theme) then you can establish yourself as an expert and take advantage of the extra exposure this generates.
List of Article Directories
The article directories listed below are highly ranked by Google and appear to generate the best inbound links. You should seriously consider submitting monthly articles to each of these.