StumbleUpon has huge traffic potential. Some days we get 5 visitors from SU, but other days we get 1000s, just depends how many thumbs up you get. Facebook is also very consistent. We also see sizeable traffic from niche specific sites such as BizSugar and Sphinn.
you can use Facebook, Twitter, Digg these are very powerfull and quality traffic source. beside you can use some of Social bookmarking site
Probably the best is Facebook or twitter. I found that FB has a massive traffic and quite easy to promote your website.
Well there is one more new social network on the chart, called Hacker News. This site has actually given me 30% of my total traffic since last couple of months. Also if you do proper bookmarking in all the sites which are there in the addthis widget, I am sure you will get the traffic you desire. Obviously for a quick traffic networking site would be Facebook, however you have to implement a proper viral marketing campaign to promote your site and get the traffic
A more popular and better social media tool that can aid in generating more traffic is Facebook. The fan page is very convenient in traffic generation and in promotion as well.
LinkedIn can be a useful tool too; it has excellent targeted advertising so is great for getting the right sort of traffic which converts. It is a different audience to Facebook and Twitter; it is more corporate and professional, so if that suits your market then consider that too.