I am surprised no one mentioned Reddit. Reddit really helped me gain perspective. For one thing, it made me realize how similar people all over the world are. No matter how specific a post is, chances are really high that someone else will chime in and echo the feeling/experience that has been expressed. In short, the positive message is: You're not alone! For another thing, it is (despite the horrible search functio…
Other than my country's subreddit I can't think of anything reddit has contributed to my life, for the past two years. I go there daily, but I almost never find anything interesting I haven't first seen elsewhere. It's a neat place to waste time, but even on small obscure subreddit, the content just isn't there anymore. I guess you could say it changed a lot of lives, by becoming "the front page of the internet", but…
/r/StopDrinking also helped me help my friend regain control of his life. /r/fitness helped me regain my health.
Then there's /r/randomkindness, /r/bestof, /r/askreddit and /r/cscareerquestions.