One of the main goals with article marketing is to gain incoming links from outside sources for your website. A common SEO strategy includes having links at the bottom of the page in a signature and/or within the actual content itself, depending on the requirements of the article directory.
One of the main issues with article marketing is the actual websites that they are listed on. Many of these article websites can be of low quality. While there can be some good article websites, those are far and few between. The best source for your quality content is on your own website. Another problem with article marketing is that these pages will be found on other websites so you will have duplicate content and duplicate anchor text and links from other low-quality pages.
It is much better to focus on good quality content that people are interested in, content that people will find interesting, and then people will choose to link it is organically/naturally. These links will be much more beneficial to your website rather than going out and artificially gain 5, 10 or 15 websites to post your article on.
In the end, the best choice for your content/articles is on your own website or blog. Keep this quality content for yourself and the better the content, the more links your site will naturally gain from the search engines and thus this will help your organic rankings better.
Out of all the article marketing sites that I have come across, one that I do like is ezinearticles.com. You can submit up to 10 articles initially, and then your content will be reviewed for quality, and if their guidelines are met, then you can submit more.
But that being said, save the best articles for your website, use social means to help push your products/services message. If you can manage to write an article for a well known industry website, newspaper or magazine, then this would be a great choice for overall exposure. Essentially, a lot of the times it will come down to the quality of the website that will be linking back, the relevant traffic that it