Just found this guy Jack Humphrey. Seems to know his stuff.
Remember the Pereto Principle? 80% of your income comes from 20% of your subscribers. Means (if you take it on out a step) that about 64% of your income comes from 4% of your subscribers.
Now, given that there are maybe 500 article directories, around 20 article directories will give you the biggest bulk of returns for your article submission efforts. After all, your time is very valuable.
I've included the links (although not "hot") for your use. They are live on his site - but the cut and paste into "Blog This" doesn't capture the links.
Top 21: The Best Article Directory List:
Article directories are a dime a dozen. If you are going to do it the hard way, meaning you'd rather submit one at a time and not use the best article syndication service I have ever used, then focus on submitting your articles to the top 21 article directories below.
You won't benefit from the long tail effect of submitting to the other article directories available, but you will at least hit the big ones with the highest Alexa and Google rankings.
1. http://www.ezinearticles.com/ EzineArticles
2. http://www.goarticles.com/ GoArticles
3. http://www.webpronews.com/ WebProNews
4. http://www.articledashboard.com/ ArticleDashboard
5. http://www.searchwarp.com/ SearchWarp
6. http://www.pubs.acs.org/hotartcl PubsACS
7. http://www.articlesbase.com/ ArticleBase
8. http://www.isnare.com/ Isnare
9. http://www.buzzle.com/ Buzzle
10. http://www.articlecity.com/ ArticleCity
11. http://www.ideamarketers.com/ IdeaMarketers
12. http://www.site-reference.com/ Site Reference
13. http://www.articlealley.com/ Article Alley
14. http://www.web-source.net/ Web Source
15. http://www.amazines.com/ Amazines
16. http://www.submityourarticle.com/ Submit Your Article
17. http://www.thewhir.com/find/articlecentral TheWhir
18. http://www.excellentguide.com/article/ Excellent Guide
19. http://www.directorygold.com/ Directory Gold
20. http://www.articlesfactory.com/ Articles Factory
21. http://www.contentdesk.com/articles.php Content Desk"