Surprised this hasn't been a topic yet (maybe I missed it).
My favorite thing for a girl to be wearing is a turtleneck/sweater, they're usually lose and short which make them great for accidental belly showings when they stretch/reach for something or even on purpose showings.
The next best is a girl in a business suit or jeans with a blouse that stops right at the top of their pants so when they raise their arms it shows a lot of their belly, the best being the belly button.
Post your pictures/videos of these two types, stretching/accidental belly showings are my favorite.
EX:
http://www.agefotostock.com/age/en/Search.aspx?query=smiling%20navel&author=Boccabella%20Debbiethis is a link to my favorites on a photo site, all stretching navels
http://www.agefotostock.com/age/en/Lightbox.aspx?lightboxId=975266&se=FechaCaducidad&sd=Descendinghttps://www.youtube.com/watch?v=pnpfW-X9kLg&list=PLFF46ACD9E91896490:50