Most people submit to directories for a good quality backlink. But before you submit, you may need to know if its worth submitting to. Google the big search engine and traffic provider don't give quality to all directories. With so many, you need to know how to determine. Basically what i do is determine how many pages the site has listed on google and compare this to how many pages the website actually have. You will be surprised. Even though a directory has pr, this does not mean that the page are seo friendly and you will get a link back. 1. Make sure the pages are seo friendly html pages. 2. See how many pages they have listed or indexed in google. To do this go to google and in the search bar, put in site:www.thewebsitename.com You will be surprise that many site don have little are no pages index. These index pages are the actual pages that you backlink make be on. IF there are no or little pages, changes are you are wasting your time. THis applies for article directories as well. Most site says they have 10,000 to 30,000 articles, see how many pages are really indexed. Probably little and what this means is they probably got a free database of articles and added them to a website.
Also beware of supplemental listings. And don't care about those boasting about their Alexa rank, it's mostly caused by submitters, not by visitors. It's easy to move to top 100,000 and still have no real visitors (except submitters).