There are hundreds and hundreds of search engines and directories on the Internet. Any of them can bring traffic to your site, but only about 14 of these sites will ever bring you any meaningful traffic. Probably only a handful I bet.
Most people only visit search engines and directories that they hear of often.
They use the sites that are constantly promoting their databases - on television, radio, and in newspapers and magazines. So I focus my promotion efforts on those top search engines. This is the best way to get listed in these top sites, and the only way that I'll ever do it. In fact, if your web site is for a business, sites like Yahoo will never list you if you use such a program. Beware of companies that claim to submit your site to 100's of search engines and Yahoo for anything less.