Article marketing is very important part of creating a presents on the search engine. I use over 50 article directories in my SEO efforts. I would have to say my top 10 would be

EzineArticles.com
GoArticles.com
ArticleDashboard.com
SearchWarp.com
ArticlesBase.com
iSnare.com
SelfGrowth.com
Buzzle.com
ArticleCity.com
IdeaMarketers.com