Twitter is probably the social media tool I post to most frequently. With close to 700 followers and 700 people I follow, I enjoy the quick and easy perusing of other people's tweets, the sharing of interesting / useful / important links, and the witty repartee that can result. Since joining in 2008 and initially making fun of it, I've come to embrace the challenge of saying something meaningful or interesting in such a small number of words.
I've found a good mix of Twitter accounts to follow that both give me access to articles, ideas and resources I know I'll find interesting, and accounts that challenge me to think differently about the world. I try to follow at least one link every day to a resource/site/article that I know I'll profoundly disagree with.