Facebook is hosting its annual f8 developer conference in San Francisco today. Think of a room full of young programmers all chomping at the bit for the latest and greatest from the site that now has over 400 million users – yeah, it’s exciting.

Mark Zuckerberg (founder of Facebook) just finished his keynote, wherein he announced some very extraordinary new developments. At the first annual F8 event, he introduced the world to the “Social Graph,” which mapped out people and their relationships. Today, Zuckerberg presented the “Open Graph.”

Your online identity isn’t restricted to just who you are and who you know. It also includes restaurants you enjoy (Yelp!), movies you like (IMDB) and the music you listen to. With that in mind, the Open Graph takes all these parts and connects them to create a more socially aware environment to offer personalized experiences everywhere they go. I know, it blew my mind too.

So how does that work? Let’s say you visit CNN.com and check out an article that interests you. Now, you will also see which of your Facebook connections “like” the article as well, and you will also have the option to “like” it. 30 partners will be launching this today. This new development doesn’t require you to login or anything – the site just knows.

It’s actually kind of scary when you think about it, and I have the feeling that many people are going to react with similar apprehension. Let’s see where it takes us though.

Top announcements to note:

• Open Graph Protocol – connects sites like Pandora, Yelp and CNN with your Facebook profile making more personalized experience
• Graph API – makes it simple to read and write connections
• Social Plugins – makes your site instantly social and personalized without any code
• Like button – iframe goes where you want it on the site and then you’re set
• Social Bar is the kitchen sink of Facebook plugins
• Facebook is adopting OAUTH 2.0 Standard

UPDATE: Changes already appearing on the Facebook homepage!