Social bookmarking has become more and more popular on the internet. According to this trend, our WordPress has also plugins that help us to accomplish this without putting forth too much effort.
This concept is pretty simple. Social Bookmarking is when people who like your product (articles) literally bookmark that product on a Social Networking site. StumbleUpon, for example, lets users setup an account and bookmark sites. With Digg, users submit their product and people can digg (favourite) it, as well as comment and further share it.
I chose Sociable (the first one above) for my blog because this plugin is very easy to use, it supports actually 96 social sites (include email and print links) so your readers can bookmark your articles quickly. But why did I put a few of them ? Because too many icons will make you blog be in confusion so I choose those I think it's popular.