A humans.txt file is a simple text file which gives credit to the people behind building the site.
It is stored at the root of the site like this one https://www.google.com/humans.txt
I only heard about this recently when someone commented on my article 7 simple tips to improve your .NET website, saying I should included it in the list. While I don't think it improves your site, I do think it is a good idea, and I've started looking for them on other sites. I like to call it "humans.txt spotting".
Now I know what they are, I find it surprising how many big sites don't have one. Some of the ones I have found so far have been quite imaginative. Here are some of my favourites:
This one is cool because it seems to be the start of a text adventure game.
Have a look around the internet and let me know in the comments if you find any good ones.