I want to make some new friends outside of my current social circle. I'm looking to meet smart and open minded people. What are some activities I could do or groups I could participate in where I'm likely to meet such people?

I'm particularly interested in personal experiences meeting people, rather than speculation, e.g. "I imagine ballroom dancing would be great" is not as good as "I met my partner and best friend ballroom dancing."

Also of interest would be groups where this is bad, e.g., if ballroom dancing was no good then "I never made any friends ballroom dancing, despite what I initially thought" would be a useful comment.

(I have a small list of candidate groups already, but I want to see what other people suggest to verify my thinking.)