The top social media sites that you should be using: Facebook, Twitter, Google+, Pinterest and Instagram. In case you need to market your self for a Job or you need to market your company then you should also join LinkedIn.
I will suggest you that Facebook, Twitter,Linkedin,Google+,Pinterest,Myspace these sites are best social network sites.
Try On Reddit.. there billions of traffic there. if your content is good u will surely got clicks/ visitors.
Social networking sites are the sites that really plays a very important role in building up the business,some of the popular sites are facebook,twitter,linkedin,google+,pinterest
Lot many social networking sites are there that used to promote your business, but the point that we keep in mind is, the activity we do, Concentrate few social networking sites and keep updating the information regularly in daily basis