In many cases, we as SEO engineers know how to evaluate a potential link or directory to get the maximum benefit for a website. Many of these sites are broken up into very specific sub-categories. Sites such as DMOZ, the Yahoo Directory, Go Guides and many others are called authority sites. They have been on the web for many years, some from as early as 1997. With the age of the site, the search engines have found that these are not fly by night Spammer sites that just want to host Google AdSense to make money. A lot of directories are human edited so not every site will get in on the first attempt. These are the sites that are worth going after in your linking efforts. They are the kinds of sites we recommend people submit their sites to.
At first glance, a directory or link site may not look like much, but if you dig a little deeper, you can probably find a category that will fit every business type. The key to submitting to these types of sites is finding the most relevant category for your company. And, remember, even if there is a category that is similar but not exact, it is worth submitting to.