Directory submissions, if done to the pages that are relevant to your website, will help you gain some credibility in the eyes of Google. These are external links, and if they have good PageRank and are from "good" directories such as Yahoo, botw.org etc, you will see ling term benefits from these external links. Do not expect traffic from here, just "external PR".
As fasr as facebook goes, if you have an facebook account or a facebook application and it gets popular, you will get a lot of attention from the facebook world. Compete.com just published its January numbers this morning and reported that nearly 134 million US web users visited Facebook last month. Google saw nearly 148 million. So if you get some traction on facebook, you can see how much you could gain!
I hope this helped. Let me know if I can explain more.