Do you use Twitter, Facebook or Youtube to promote your website ?, and still confused on which one can get you more traffic ?. Here is a handy chart from cmo.com, which will answer these questions. It covers twitter, Facebook, flickr, LinkedIn, YouTube, digg, StumbleUpon, Yahoo, Reddit, del.icio.us.
Read more and get the PDF
Amit Agarwal at labnol.org says some of the ponits are not valid anymore like
your site won’t derive any SEO benefits from Flickr or delicious.com as they nofollow all external links.
Read more on labnol.org