Authority Web Sites are Those with high PR (at least 6+) that Google Loves. These web site pages easily rank on Google.
As a example,
In screenshot above you can see that webmd.com is a authority web site and it's niche is weight loss. So if you can get a web page created on webmd.com on weight loss topic you will definetely rank on Google with out much backlinks and effort.
There are hundreds of Authority web sites , I'm using Amazon, Lulu, Free-ebooks.net on my affiliate marketing products.
Here are some Authority Sites,
http://amazon.com – product pages
HQ News sites (There's countless numbers of news sites you can use as Parasite) – through PRWeb, SBWire, PRLog etc
But as for my knowledge,
You should try Buzzfeed.com It's really easily rank Google on Buzz Feed.
Another thing is like facebook.com, is a authority site but it does not dominate any specific topic or nich like weight loss. webmd.com as above dominate weight loss niche. So you could get a some hard time to rank web pages ( like fan pages of facebook) on Google if your topic is doesn't match with facebook authority niche.
If you take Amazon, it dominate niches like books, hard ware, electricals and so many niches. Just Google Curved LG TV you will see amazon result with in TOP 30 of Google results.
So finally, The Authority Sites Have High PR(6+) and Some Authority sites dominate Google for specific niches and Some Authority sites don't.
If you want to rank on Google You will have to find a Authority Site which specifically dominate Google for a particular niche. But for low competitive keywords most of authority sites rank well with out much of backlinks and social singnals.
So Now create some pages on Above Authority sites and add to google index and See for your self, How easy is to rank on Google.