From RT:

If you want to block facebook, you’ll have to edit your hosts files with this information. You can also use Adblock Plus, Ghostery, Collusion, BetterPrivacy, disconnect, and/or NoScript.

These addons are mostly for Firefox. If you want the Chrome version, go to the Chrome Web Store and do a search for their names and install whichever ones you want. If you already use Adblock Plus, you can add this link to your blocklist.