I preface this by saying I have not yet submitted any articles to any of these sites. This is what my research has turned up, mostly by recommendation from others. I intend to start submitting articles to some of these, and can report back on the progress. There are a lot more than the sites below, but this should be more than a good start.

These are the big article submission places for traffic-building:

ezine Articles

http://www.goarticles.com/

http://www.articlesbase.com/

These may not be what you were looking for, but are article submission sites that offer pay options:

http://www.ehow.com/

http://www.associatedcontent.com/

http://www.brighthub.com/

http://www.helium.com/

http://www.suite101.com/

Another similar way people generate traffic, making sites or writing articles on these kind of "Page-building" sites. Most offer AdSense or Amazon Affiliate spots to add revenue to the sites:

http://www.hubpages.com/

http://www.infobarrel.com/

http://www.squidoo.com/ (Seth Godin's Company)

I've tried Evan Carmichael (http://evancarmichael.com/) for one article. The site is geared specifically towards entrepreneurs, so it may not work for your purposes. Anyways, it didn't drive any significant traffic to my site. One advantage of article marketing is that it may improve search engine rankings, although it is difficult to attribute any improvement in your rankings to one specific source.

I have heard from other people that they've had luck with eZine Articles, eHow and Squidoo. I'm pretty convinced that writing guest posts on blogs is the better way to go in most cases.

Though I don't have a lot of experience of it myself I'd second Corbett's suggestion that guest posting on blogs relevant to your niche is the best way to go to attract an audience interested in what you've got say.

Having said that, if you're heavily SEO optimising your articles the added clout of some of the article directory domain names probably carries some weight. I've heard a lot about ezine articles and squidoo although I think they serve quite different purposes.

How about posting the articles on one of your own blogs or article-based website?

It's the long way around but if you do it this way, you build up another web property that has value.

If it's a blog, then you can promote it any way you would promote a blog.

Hand downs...

Commenting on other articles Joining link alliances (people who promise to review & promote if applicable on their sites) Guest Posting

StumbleUpon Twitter Digg

Article directories like the one's mentioned already are great, but don't expect a significant, constant flow of traffic from them. The real reason to submit articles is for backlinks from sites with a high page rank. Make sure the directory offers "do follow" backlinks.

I strongly recommend Biznik. It's a leeeetle bit like the slightly more laid-back cousin of LinkedIn. If LinkedIn is "bigger and more corporate," Biznik is "smaller and more entrepreneurial."

I got a big spike in traffic when I posted an article to Biznik (they even wound up putting it on Biznik's home page for a bit, which was fantastic). Plus, the community there is great--you might sign up with your main intent being article posting, and wind up making some terrific connections in the meantime, giving you the short-term pops in traffic when you post articles and the long-term increases in traffic as you interact with people and build your network.

There is a user-ranking system at Biznik that is a "plus" as well. If you write quality content, other users will give you a good ranking, which makes your article show up higher in the Biznik search results, and lends an immediate stamp of credibility to your article.

I use an article spinner to spin articles that are similar but not exact content. Then I post the original on my blog, and submit the others to directories over a 2 week period. It is not advisable to submit the exact same article to multiple sites. Google just ignores them. My goal is for getting indexed with specific keyword searches.