My sister and her family were fortunate enough to recently get a private tour of the White House. They simply wrote to their state representative and requested one.
She found it just as interesting to go through all the security before entering, as the actual tour itself. While each family member had to go through the standard metal detectors and pat-downs, she found the last step of security the most interesting.
Each family member had to individually enter a small room and stand in front of a fan for a few minutes that was blowing toward a screen. On the other side of the screen was a dog sniffing the air.