The difference between a directory and a search engine, is a search engine is an automated list of everything that it can find. A directory is an ordered list of sites generally examined and added by humans.

Yahoo is the best known directory, and getting listed in Yahoo is essential to improving the number of hits on your site. Getting listed in the other large directory can definitely increase your hits also.

Traffic equals Yahoo. That’s a good equation to understand. Get your site listed in Yahoo. Some things to remember when submitting your site. (1) Do not submit more often than once a month or Yahoo will not look at your site, (2) Be sure and pick an appropriate category (only one), (3) Don’t write in all caps, (4) Keep your description short, (5) Use relevant word in your description, (6) Be patient, these are human beings reviewing your site and they have a large backlog.
Sites within Alaska and Canada.
One of the first directories on the internet.
A good directory.
Another good place to get listed.
Submit here for some more traffic.
A massive listing of human-rated sites.
Starting Point
Starting point accepts all submissions of new sites, then ranks them based upon your visitor votes.
Whats New Too
A site useful to announce your web site to the world.
Moldovan Directory
This directory is a listing of new sites. The directories are very active, but are archived so you will remain listed for quite some time.