The two best social media sites you can use to drive targeted traffic to your website are Digg and Facebook. Despite both being quite radically different together, they get huge traffic and work in a way that your material can go viral fast. 

Digg lets users follow each other (much like twitter) and post links which are put forward and dugged by registered users and followers of your profile. Generally the more diggs a site gets the more visits your site will get (although you’re likely to get many more visits than diggs).
How To Use Digg:
Step 1.

Sign up to Digg.com
Step 2.

Start commenting on diggs – I’ve found this to be the easiest and quickest way to gather followers.
Step 3.

Follow others – by following other people (particularly popular diggers) you’ll not only gain more followers but also have improved chances of getting other people to digg your content. By following other people your news feed will change to show their new content (and vice-versa).
Step 4.

Once you’ve gathered a solid group of followers you should submit your link (Shown top left right of the Digg logo) you should try and post with an intriguing headline.
You really need to contribute to the digg community if you are to get repeat traffic from the website as this way more people will see your link and promote it.
Once you’ve submitted your link its simply a waiting game to see how much traffic you get! Try experimenting with different types of content to see what works best. I’ve also found Digg an excellent way to get pages indexed into Google (usually within 12 hours).
Now we more onto Facebook there are numerous ways to get traffic to your site via Facebook however if you’re not careful most will be limited untargeted traffic.
The best methods are creating a fan page of your website/blog (only worth doing if your website/blog is already getting at least 200 visits a day with a good portion being returning visitors) or by creating a fan page/group at your websites theme i.e. if your site is about cat food you could make a fan page on a certain breed of cats.
How To Set Up A Fan Page
Step 1.

Visit Facebook.com (no need to sign in or register yet) and click “Create a Page for a celebrity, band or business.†(Shown highlighted below)
Step 2.

Select “Cause or community†– name your community and click “Get startedâ€
Step 4.

Log into your Facebook account (or create one at this point).
Step 5.

Now you’ll need to add an image (try to make it very relevant) write some content on the wall, invite your friends (only select those who are interested in your fan clubs theme) and finally “Like†the group yourself) this will show the group on your news feed which will encourage your friends to like the page too which in turn will then show up their friends newsfeeds and so on (as you can see this is really is viral friendly!)
Now when you combine the above together along with other social media sites you really are boosting the chances of your site to go viral, just remember you can lead a horse to water but you can’t make it drink i.e. if you post boring content don’t expect the world to fall in love with it!
Share This
You should also consider adding a “share this button†to your website. You can grab the code from: sharethis.com. This gives you a small widget to add anywhere you like on your page which enables people to quickly post your link to Facebook, Twitter, Digg (and many more social media sites) potentially increasing your traffic.
Share this offers multiple looks. The most popular is:

Simply visit sharethis.com and click “Get the code†(shown in yellow below) add the html code (I find this better since it’s more customisable than downloading the WordPress plug-in) either to the bottom of your posts/pages or in your sidebar.
Sam White has just released a free report teaching you how to drive quality targeted traffic to your website download it at: Drive Huge Traffic To Your Website – Free Traffic Blueprint