I've spent some time finding directories to which you can submit your web site for free. Some of these are instant, which means you create an instant backlink. Others require approval. Obivously there are advantages to submitting to both types of directories. The instant submission sites tend to become "link farms", and have lesser Page Ranks on Google. The reviewed sites tend to have better quality sites listed, and have higher Page Ranks. You'll notice that dmoz.org has a Page Rank of 9. Anyhow here they are. Hope this is helpful.