Although not as great as they once were, directories still provide one-way links to sites. The good thing is that many are free and do not require a reciprical link.
Also, directories gives you a backlink, thus giving your site more visibility around the search engines and to be crawled more frequently by spiders.
They are easy to find and submit to, often are very cheap, get you a quick one way backlink and maybe the odd visit or 2 - can't complain!