That's easy. None. I have a pretty good fixed base phone here at home that fills most of my needs. Then there is email, and voice mail to a lesser degree. On the fringe are the very few forums that I visit. The most important is face to face contact. No social networking could possibly measure up to the full week on the outer banks of North Carolina in the same house with 29 of my closest relatives. It was the experience of a life time.