There have been one or two tweets from writers and developers about there being easter eggs on this site. I haven't started looking for them yet, but I wanted to start a thread where they can be easily compiled. If you find one, I'll update this post with credit and directions!
1. This may or may not be considered an easter egg, but it's arguably hidden, so I am writing it. On the top left or top right of the screen, on the persistent navigation bar, there is a triangular button that shows up when you roll over it. If you click it, it snaps you right to the top of the page you are viewing. (BatmanNewsChris)
2. Type 'cow is watching' into the search bar. Don't press enter. (dan and toby.bloem)
3. The Konami code! Enter this with your keyboard: up arrow, up arrow, down arrow, down arrow, left arrow, right arrow, left arrow, right arrow, B, A. Watch the navigation bar. (Liridor)
4. At http://www.polygon.com/pages/about, type 'iddqd' without quotes. (cdutson)