Many SEO experts recommend submitting your website to many link directories such as DMOZ.
IF (and it’s a big if) your website is accepted for the directory you’ll gain a text link or two.
This route to gaining backlinks can be a lot of SEO work and a lot of directories expect a link back (from the home page seems the norm which should be avoided for SEO reasons) for their link!
Link Directory SEO Value
Unless you have an important site (then you won’t need text links from link directories!) you’ll probably find your link deep within the navigation structure of the directory on a low PR (PageRank) page.
Don’t make the SEO mistake of seeing a PR8 home page for a directory and thinking your text link will pass PR8 benefit. You won’t get a link anywhere near the home page, on the rare occasion I’ve submitted sites to directories it’s lucky to receive a PR4 link, most are PR3 or less!
Directory Link Value
Have a read about the PageRank calculations for reciprocal links (near the bottom) and you might understand why most directory links pass so little link benefit they are worthless links.
You may realise I’m a tad negative about gaining text links through link directories (I don’t submit any of my sites now).
The negativity is because it takes so much time filling in forms etc… for what are mostly very low quality links. Save your SEO clients some cash (they have to pay for your time) and don’t offer it as an SEO service.
If you decide to go the submit to directory route there’s plenty of sites that list various directories you can submit to, both free submission and paid.
Personally I’d never pay to be submitted to link directories, they hold so little value due to the depth of the links and number of links from each page.