From eBiz101.com
Directory Search Engines differ from traditional search engines in that directory listings are sorted by humans. This can be good or bad for you.
It's good because humans almost always do a better job at sorting the listings than do computers. So if you have a site that specializes in pet hamsters, it is more likely that a visitor to a directory search engine who searches for "pet hamsters" will locate your site's listing. But it also means that if your site is about pet hamsters but it provides very weak content or little usefulness, these humans will decide not to list you at all in their directory.
If you are interested in submitting to the many popular directories such as LookSmart.