Using directory submissions services, you can ensure that your website is submitted to good directories which are regularly indexed by all major search engines.
it will help your website in 1. properly indexing in all search engines. 2. will get good number of back links at a very low cost and in very less time. 3. will help in increasing PR of your website as most of the directories are PR3 or more and finally, 4. it will help in bringing some traffic to your website.
hope this helps,
let me know if you need any other details on same.