This one was a bit more difficult than I'd first expected. Aside from family, I have quite a few friends who ebb and flow through my life. I've moved around a lot, and I become closer with some friends at different times due to logistical issues such as proximity. Although Facebook and Skype have certainly affected the ease with which I'm able to keep in touch, I still notice that at times I'll be more involved with some friends and less with others.
That said, there is one person I've known for (*cough*) over 30 years now; she and I haven't always gotten along (pretty much a prerequisite for family), but as I have gotten older the rough edges of our relationship have smoothed away, and she's usually the first person I call with good news or bad.