first,my sites : http://www.qwesz.com http://www.qwesz.com/articles-directory then : ezinearticles.com
Ezinearticles, however, I've found that once submitted to ezine, many other directories pick up the article for their inventory. So, if you are limited on time, post to ezine, then search for an exact phrase in your article and watch the list of postings increase. Allow some time as it may take a week or two for the page the article is on to get cached.
The best thing 'for links' to is re-write your article for each directory. This reduces the chance of it being looked at as duplicate content and only counted once. But..............what a pain!
Huh? The purpose of article directories IS duplication. Others download the article and post to their site.