Artist Spencer Tunick staged a record setting group nude photo in Mexico City's Zocalo Square. 18,000 people posed for the photograph, as police and no-fly zones kept the onlookers at bay. Tunick is famous for similar shoots in Germany and Spain.
And while we're delving into NSFW territory with a little nudity, here's an interesting blog submitted to me by an artist simply titled, "Sex in Art". 18 and over only, please! The site does contain some graphic imagery, and as a precaution, I'm linking to their disclaimer page.