Facebook has a vast amount of applications in store... but the vast majority is useless in my opinion. But the fact that all the application come from third parties is impressing and aligns completely with the idea of Web 2.0. Nevertheless, you already have a mess on your "dashboard" (when you logged in) if you have more than 20 active friends. However, with the announcement of Google's OpenSocial more applications will come and most of all it will be easier for developers to create applications for various social sites such as Facebook, Ning, Hi5 and more by working with one single API. With the rapidly growing number of social apps you better keep track of SocioApps, a London based web development team working on social application mainly for Facebook but also develops for other communities by using OpenSocial.
I am now going to remove the "Which Friends Character Are You?" because I do not think that I have the character of Monica :)