This depends on the type of website that you have, what type of audience that your website is targeting and where are your audience hanging out on the Internet.
There is no "do this and get more traffic" formula. You have to answer the questions above, test out different tactics for each of the mediums and continuously measure whether the results you are getting are worth the efforts. Also, if the website that you are driving traffic to is a business website, then you shouldn't be looking for a way that drives the most traffic, but a way to drive visitors that are the most likely to become a customer.
From my experience, unless you are offering a very cool product or service with raving fans, you will need great or at least useful content in order to do well on bookmarking sites and social networking sites. As for directories, they are slowly going away. Only submit a site to a directory that is well-branded or widely known among the community that you are trying to target. Directories built for SEO are basically on their way out.
Using all of them without doing your homework will cause more harm than good. Spammers tend to submit all the pages on their websites to all the social bookmarking, social networking and directories on the Internet. I don't think this worked for them.