Twitter, I read more than I post. It is integrated into my works IM program, and I get current local news feeds come through from such places like the Standard newspaper. It is also the only social network I can access on my not very new phone, because you can post by sms text. A lot of celebs use, sometimes they answer if you send messages to them. Certainly I have gotten to have a few words with people I never probably would without it, an example was the other night I had few brief exchanges with Lady Bathurst about the movie The Expendables