One of the most important things that you need to do, after completing the website, is submission to popular directories. Directories differ from search engines, in that the former are human edited. Two most important human edited directories are ODP (dmoz.org) and Yahoo (yahoo.com). ODP submission is likely to take quite a lot of time, anywhere between 2 weeks to 8 weeks. ODP (Open Directory Project) does not charge for submission or inclusion. Yahoo business site submission costs about US$300 per year.  Yahoo also accepts free submissions, provided that the website is non commercial. It is important to remember not to submit often, as this might be regarded as spam, and your site may not be reviewed at all for inclusion. There are several other less known directories, such as zeal.com which are worth submitting. Note that zeal.com requires that the submitter pass a qualifying test!

Update:

As on November 2011, Google has stopped showing the Google directory entries, and considerably reduced the importance of directories listings. It may be worthwhile to submit only to a handful of useful and popular directories rather than to submit to the entire list of directories.