A really hot topic at the moment is whether or not the Google +1 button affects rankings.
So what is the +1 button?
Google gives this short but great explanation:
“The +1 button is shorthand for “this is pretty cool” or “you should check this out.
Click +1 to publicly give something your stamp of approval. Your +1′s can help friends, contacts, and others on the web find the best stuff when they search.”