I came out and told my parents I did it. I felt it to be a huge relief for me as I was no longer doing it behind their backs. Not that doing it in front of their faces is any better, but they didn't get half as angry or disappointed as I thought they would.
All my close friends know (some use as well). As for other not-so-close friends, I will only tell them if they ask me. It's no big secret, if they assess our friendship based on that, I know they are not worth my time. If not, I keep it to myself.
My boss and all co-workers know, but I work in a surf store, so drugs is almost a prerequisite haha.