Facebook App Center is now at last available to us folks in the UK. It's been out in the states for a month or two now and is a place for the most popular web and mobile apps which use Facebook integration.
It's actually a brilliant place to find new apps to play around with, or use as tools. You also get personalised recommendations based on what you're friends are using, it'll even tell you which friends are using them.
You'll be able to access apps in many different categories, ranging from games to utilities.
It should be rolling out to everyone slowly, don't worry if you don't have it yet. But you'll find it in the left sidebar on the homepage under the "Apps" section.