I'm doing lots of directory submissions for my websites and having some great results with it. Some people say that directory submission is not that good for backlinks as it was few years before, I disagree on that.
You need to build backlinks from dirs as well and you need to submit youe website to as much as posible dirs you can. Also you need to find niche related dirs and submit to that dirs also, this is veyr imortant, if is dir of good quality and your niche related you can even consider to pay for inclusion.
This is great Directory of Directories where you can find niche related dirs:
http://www.web-directories.ws