This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
As there are lot of things you can do with Facebook API- You are trying to authenticate user based on Facebook credentials? or are you trying to create commenting system and lot other things which come with it for your application? Or are you trying to do other things? In any case for you to use Facebook features in your web applications you would have to create a Facebook Application.