I have to agree with the comments around articles being written primarily for the links they can generate to your site. Writing an article a day to place on your own website is great for generating more content that you can rank for, and those articles should definitely be top notch.
But, I think the original question was more about how to best submit articles to directories that won’t get hit with duplicate content penalties by Google. The strategy for this is writing one good article and then spinning it multiple times for each of the directories. This was actually a new concept to me yesterday, until reading through the hub pages article, which leads you to an article spinning website. The site is actually fairly decent and seems like it would work well. I’ve taken one strong article, spent 4 hours on setting it up in Jetspinner and now have hundreds of unique articles that can be submitted to directories. Will have to see if it is worthwhile, but for 4 hours of time, the most I can loose is the time (and a few bucks for the submission service).
In the end, as bad as it may sound, more links are more links when it comes to SEO. And the more links you have, the better off you will be.