Submissions to directories can be an effective method to boost your websites ranking.
Google the leading search engine places significant importance to text links that contain key words (also known as anchor text links)
Google places particular importance on links on pages of a redial there.
Provided a directory has suitable categories and sufficient content for Google to classify its theme then it's probably worth submitting to.
Paid versus free listing?
There are literally 100's of free directories out there, so you don't have to pay.
The larger and more popular directories such as Yahoo do charge and dependent on your budget this may be worthwhile, particularly for e-commerce related sites.
Some free directories (my own):-
Best of luck!
About the Author
Clare Lawrence is CEO of Discount Domains Ltd - A leading UK provider of Domain name registration and Web Hosting services. Please feel free to re-publish this article provided this reference box remains together with a hyperlink to http://www.discountdomainsuk.com Clare can also be contacted on firstname.lastname@example.org