If you are going to submit your site to a directory you need to ensure firstly that it is a legitimate directory and not a link farm designed to trick the search engines. You also need to determine if its going to be of value to you. 

Look for industry related Directories in which to list your site. Obviously if the Directory has a high Google Page Rank this will certainly be of benefit to your site.

When you do find a suitable Directory of course it’s equally important to ensure you actually list your site in the correct category. To do so can mean the difference between success and failure.  Submitting your site in the wrong category can mean your site being totally lost in the void.