I have been reading several threads about making friends on the forum, and it reminded me of how I used to make lots of friends. I recently came back to SL, and wonder if it will still work.
I would go to a busy dance club (or Live Music Venue), where of course 90% of the people were standing around alone. I took an existing friend and we went straight to the middle of the dance floor and started dancing. Then we IM'd several people standing alone and invited them to dance with us, by asking, "would you like to dance with my friend(s) and I?"
The majority said yes, even those who were "offline" just listening to music. It was totally non-threatening to anybody (including to me, doing the asking). Some would join my dance hud; some would chat, some were quiet; often we made a group chat.
Everyone met new people. I made a note of who joined and later followed up with some. So the next time we chatted, we already "knew" each other. I started many long-term friendships that way.
Seems like it would work today as it is still non-threating. Anybody can join without worrying about chatting, sexual advances, etc.