From a search engine optimization standpoint, most link directories aren’t worth the time, effort (and often money) spent in getting your site added. However, there are exceptions.
SEO Company has a useful list of the top 40 or so web directories rated by inbound link quality. This is worth bookmarking should you ever need to quickly get some quality inbound links to a site.
If you’re not sure about the value of link directories in this day-and-age, SEO Book has a good article about whether they are still relevant for SEO purposes. In short, yes, if they are quality directories.
Most of the top directories listed require a fee to get your site listed. However, if you’re not willing to pay for a listing there are five that will list your site for free:
So, if you’re looking for an SEO boost, it would very likely be worth your time to get your site added to these five. And, good luck getting into the Open Directory Project! I’m still waiting.