Reddit, FB, YT and Twitter. All for different purposes.
I love that reddit can be so specialized. The only downside is some sub reddits seem to be filled with 12 year olds.
I like that I can just follow people on Twitter that I'm interested in following and block others. Not ignore, really block. I'd love to see that option on Message boards.
Youtube allows me to do projects I'd never consider before. Also, Great for travel, walkthroughs, reviews, etc. Probably my favorite.
FB just keeping track of what high school friends are doing and local business. Some of the FB groups are terrible e.g. Des Moines food reviews. If you say one negative thing about a popular place, they'll kill you.