ShareThis

It's a free service and it's easy to place their social media buttons code on your site. This can help you if your blog/website pages aren't long because the set of buttons you're provided with is small and will automatically fall at the bottom of your page below your content no matter where you try to place it - this will likely not help you if you have long pages because few visitors will go that far thus limiting your viral potential. I got a little benefit from using them when my content was relatively short. Fortunately, there are better alternatives.