If the Internet is for porn, then harvard.edu is no exception.
According to ZDNet.com, a number of pornographic images and links have found their way onto the Harvard.edu domain, including NSFW images on a Law School blog (available here and here).
Other questionable material has been found on the Center for Nanoscale Systems site, the Physics Graduate Student Council site, and many others.
Unfortunately, many of the links have been taken down since ZDNet.com's original post, as indicated by their update, but you can see screenshots of the images in the links above.
Additionally, you can perform a Google site-specific search for dev.flex.med.harvard.edu for some additional surprises.
The lesson? Learn at your own risk. And don't forget to use protection.