I dunno. There's not a lot of alternatives I can think of that fill the giant niche that facebook has carved out for itself. A few years ago, I'd have said tumblr maybe, but it's gotten ridiculous over there. I quit about a year ago because of how toxic it got. Honestly, facebooks biggest holding is the amount of people on it at this point--where else are you going to go and find almost all your friends/family?
I like twitter and instagram, personally.