Are free backlink directory submissions effective for SEO?

[Craig]

You can only submit once to DMOZ (except for a regional and topical listing). You agree to that when you submit, so to submit more than once is going to harm your sites chance of getting listed.

Most sites are not accepted into DMOZ and it can sometimes takes years before they get to your site. Editors are volunteers and more sites are created everyday (and submitted) than there are editors to review them, so the backlog gets bigger.

A DMOZ listing is not worth as much these days, so do not sweat on it.
Submit once, to the one best category and move on. There is nothing more you can do. You either get listed eventually or you don't and there is nothing you can do about it.

Also, free directories are not worth much if anything either. I do not bother wasting my time submitting to them anymore.