Tons!
One time, at a fair, there was a booth selling women's tops. The "changing room" was just a curtain hanging off curtain rods. Well, it was windy and the wind blew the curtain right off, exposing a 15-year oldish girl trying on a top...she was totally topless, and was exposed to probably 50 people who were in the area. Instead of covering her breasts, she tried to hang up the curtain instead, so she was exposed for about 20 long seconds or so.
The morning of my sister in laws wedding, she was needing help with her dress--something had come undone. No one was around to help her (one bridesmaid, but who knows where she was the entire wedding), so she peeked her head out of the door and asked for my help. Basically, a string was coming undone and she didn't want to ruin her dress, so she asked me to help pull the loose string off before it unraveled. I traced the string to the front of her dress and told her that if I kept going, I was going to see her boobs. She said she was so stressed out that she didn't care what I saw. So, I pulled down the front of her dress to get the string, with her left breast exposed, but her nipple wasn't quite showing. She told me not to look at it, but I stared. I felt guilty, but what was I do to. I cut the string, pulled her dress back up and made sure to pull it out and up so I could see her nipple, too, and she didn't notice the last part.
My best friend's bikini top flew off once. Pretty basic, but 10 of us friends saw. Very lovely. She was soooo mad. So, to this day I tease her by telling her that I know what her boobs look like, even when she's wearing a winter coat.