I've had several opportunities for viewing. Based on the posts so far, I've broken three of them into the categories I've seen above.
1) As a teenager, we had a neighbor whose wife was drop-dead gorgeous. She was also pretty open-minded. They had no kids, but sort of adopted me for the summer. They took me camping and waterskiing. One time while we were swimming, I turned around to see her stand up and lose her bikini top. She just smiled at me at tucked her titties back into the top. Later, I watched her getting ready for bed. She had a great body and I'm convinced the show was unintentional.
2) I worked in the banking industry for about 5 years. At one branch I hired a teller who was a young single woman who had previously worked as a bartender. She had been on the job for about a month when she started wearing leather micro-miniskirts to work. I don't think she ever learned how to pick things up without bending over at the waist. I got great views when her station was in front of my desk (as was normal procedure with a new teller). She wore panties, but they were very sheer. I finally had to fire her because she kept doing it in front of customers (the women complained). She had a great body and I can't believe that she was totally unaware of the show she was giving.
3) The last one was totally intentional and blew me away. When I left the banks, I went to work in insurance sales. I recruited a woman who had been a manager in one of the branches that I oversaw. She was a gorgeous woman with a great personality. The funny thing is that I had never thought of her sexually while working with her in the bank. I never got any peeks because she dressed very conservatively. She showed up for the interview at the insurance office in a see-through blouse without a bra. I'll just say that she didn't need a bra and all of the guys in the office agreed. Unfortunately, she decided not to come to work in the insurance business. It's probably just as well because I had enough trouble making money in that job anyway.
Over the years, there have been plenty of opportunities for viewing. These were three of the best. But given the opportunity, I'll look again.