When you're surfing with Related, you'll often see a thin bar along the bottom of your screen that offers videos, maps, reviews and other content that's relevant to that page. When you see an item you like, you can spread the word by using the built-in +1 button
Here is a video:
Gary Price has a great write up on it at Search Engine Land.
Tedster at WebmasterWorld said, "Hmm.... sounds like it might be a way for websites to be sent MORE traffic through a Google product. Imagine that!"
Forum discussion at WebmasterWorld.