Does anyone know wich the article directories that provide the greatest impact to improve our blog traffic?
Just google it, and find the ones that get the most traffic and have the better PR rankings, and submit with all of them. Also finding ones that are relevant to your site will also help with your rankings and traffic.
I will search at google Article Directories, then use Alexa to justified those site, good article directories usually below 100K ranking. Good directories does not mean it work best for us, ezine is good but it is hard and take time to approve. New articles directory is more easy approve but it generate less traffic.
The one reason that causes the recent uprise of article directories is that many of these directories derive their income from ad revenues. Ad revenues usually come in three forms. CPM ads, CPC ads and affiliate ads. CPM ads pay the publisher on a per thousand basis. In other words, for every 1,000 ads shown, the publisher gets $x. For CPC ads, a web visitor would have to click on the ad itself before the publisher sees any money. Affiliate ads are performance based and pay the publisher only when a sale is made. There are different advantages for each type of ad but as it is not the goal of this article to discuss about ads, let's just say that the goal of these article directories is to maximize ad revenues with a combination of various ad formats.
Try to find article directories that concentrate on the same niche as your blog. I have had great success with niche article directories as they usually send me traffic that is lot more targeted that traffic form genera article directories.
The biggest source of such information is Google. You can just type in your query and you will get a massive list to which you can submit to increase your traffic.