For sports, all the time. I am a very outgoing guy, and I have no hesitation being completely nude in front of other guys, or even girls. (swimming, football, rugby, basketball, and hockey for a short time.)
I have been known to get naked at several parties, not even drunk ( I never drink ), and do standing back flips or jump tables in the buff.
I once participated in a protest against a new regulation at the university's pool against being nude in the locker rooms and showers. The new rule said that every guy had to at least cover his cock and ass, and anyone who violated lost their $250 gym membership. It was bullshit, so we got together and did a full, one-hour workout completely nude, then signed a petition amongst the majority of the male members, and voted the rule back down.
I have been to nude beaches, nude hikes, and 2 nude campgrounds over the years.
i love hanging out nude, especially now that I am on my own... Nothing beats coming home from a long day and stripping down to nothing, and only putting on a pair of boxers to answer the door or step outside real quick.
That's it for me.