Twitter for me. I was barely using it until I started my new job last year where I used Twitter to help the work account and just find it gripping, namely keeping up to date with football news, stories and opinions. I spend around 30mins sometimes going through a list I've created of football journalists, catching up on what I've missed out on since the previous day..!
Although, get infuriated by these Kicca, BreathSport, Sportslobster bollocks...
Facebook I have but use/post sparingly...just to keep an "eye" on what others are upto...