In response to questions,  Matt Cutts recently confirmed that Google uses Facebook and Twitter as ranking signals.   Have a look at  Matt’s Webmaster Central video.

He gives the impression that these social media are not huge signals at the present time but their importance should grow as time goes passes.

After weeks of work I have just finished a new list of  social bookmarking sites.  There were some bookmark sites within the  social media category but I created a new category for the bookmarks.  Here is the social bookmarking list. The info is always at its best when it is fresh.  You will have trouble finding dead links in this list right now.

In all, there are actually over 550 social media listings including a list of niche, regional listings and twitter directories.  The definitions of social networking and social bookmarking seem to overlap as many sites usually include some aspect of both.  For our social media lists I have included in the social bookmark list sites that allow you to submit your website or news story.

If your time is very important to you then you should look into a submission service. Our sister site best-web-directories.com are now using their 5 years of directory submission experience to offer a social bookmark submission service.