I know that submitting your website to online directories can be tedious and the quickest way is to pay some company to do it for you.
In my experience, I have found that doing it myself is the best practice for me. I want to make sure I am listed where I want to be listed and not on just some random site that gets less than 200 visitors a week!
Here is some information for listing your website on online directories, this information is cited from: StartupBiz http://rtup.biz/website-directory-submission.php
Here are the 3 big directories that you should submit your URL to:
DMOZ Directory Submission
This old simple website directory still plays the largest role out of all directories.
Key Website Directory Submission Points:
Become an Editor - This is one of the hardest directories to get into if you are not part of the community. Spend your time applying for editor positions of categories with no editors. Once you become an editor then you can get all of your sites submitted and published.
Start Your Title with an A - DMOZ is still working off the simple approach of ranking all submissions alphabetically. The higher up your site the more traffic and search engine value your site will have.
Best Advice:
Choose a Directory that You See is Getting Updates - Many of the editors have gone AWOL and will never return. So if you submit to a directory that has been cold for months, then your site may never even get reviewed.
Yahoo Directory Submission
What was once the foundation of the internet is still important, but it is not what it is used to be. Your website submission will play a crucial role in search engine rankings, especially yahoo.
Key Website Directory Submission Points:
Choose Directories that Have Less than 20 Sites Listed - The sites are ranked in order of most traffic off of yahoo search and they are listed 20 per page. If you are 21, then the listing serves no purpose at all.
Tailor A Page to A Directory with Less Than 10 Sites Listed - For example, you can write a page on software piracy that is not your home page and still get it listed. This is a great way to get more than one submission approved.
Best Advice:
Pay for the Submission - Yahoo does not spend much time managing their directory anymore. If you do not pay for your website submission, then it may take months to get reviewed. Choose your directly wisely and then pony up the money.
Business.com Directory Submission
This is a pay submission only, but since it is a business site only it is definitely worth it.
Key Website Directory Submission Points:
Featured Listing - If you look at this directory you can see that the featured listings are at the top. Either pay for the featured listing or choose a directory that does not have many sites featured.
Alphabetical - As you can see past the featured listings on this directory the list is alphabetical. Try and add the a or a number in front of you listing to be at the top.
Best Advice:
Pay for The Feature - This site has a high conversion ratio, so if you have legitimate business model it is worth paying to be featured and having a great title to pull the traffic.
SUp Url Submission
Our site is completely free, and there are several places to place your website.
Key Website Directory Submission Points:
Submit Your URL - This is a very popular discussion where members list their url.
BOps Section - This is a high traffic area that is constantly viewed by new members looking for new ops. You can make unlimited posts. The most recent are shown on the page.
Groups - There are plenty large groups on the website that get a large amount of traffic. Posting comments and discussions with a url signature is a good tactic.
Best Advice:
Make Daily BOps Posts - Very few sites offer a no holds barred approach like this that is free.
If you know of other directories that are not listed here please add to the list.
Have a great week

Andrea~