Hi I think it will depend of you ask to,some people like to submit to a lot others submit just for the big directories. Personaly I just submit for the principal directories. As much as I know the following are the best directories: Ezinearticles.com Goarticles.com Articlesdashboard.com Articlealley.com Articlesbase.com Articlecube.com Articleblotter.com Selfgrowth.com Articlesnatch.com Article99.com Hope this help.
Do you use the same article when you're submitting to these directories or do you have to "spin" the article to avoid a duplicate content penalty ??
With article directories it is very much a case of quality over quantity. The major directories provide actual traffic. It can be argued but difficult to measure the benefit of the less established article directories and those directories that do not offer html links back to your site. It takes the same amount of time to submit to a major site as it does a smaller one.
I recommend 1 per directory an article should only take twenty minutes or so. If time is an issure perhaps you would want to hire a writer. The only other thing I would recommend is if you really want to submit the same article rewrite it so it is not in the exact order that it was in when you submitted it to the first article directory.