Natural linking to add related one-way links to your website is an accepted method for boosting search engine ranking. Done properly, the results will be worthwhile. If you are determined to take shortcuts, consider the consequences. There are valid services who will hand submit your URL to directories, and the best will provide evidence of value for money paid.
Quick and low cost solutions may backfire because others may broadcast your site to 500-1000 or more sites for $19.95, or some similar number up to $99, with varying results. You may see ads for one million sites for some ridiculously low amount. You need to think twice about where your www domain will end up listed. A low price may not be a good price.
None of the services can guarantee you will be approved and listed to all that receive your submission. Each directory has rules, and although some will automatically add your URL, most are reviewed by a human editor prior to approval.
My advice is doing it yourself. Unless you hand submit your www domain to website directories, the quality backlinks you expect from a service company could leave you wondering if your efforts were in vain. By...