(This will add your twitter updates to your profile, and gives you an option to update your status with your latest tweet)
http://apps.facebook.com/twitter/
Memorable Web Addresses for Profile, Page or Group
(You tag which books you've read, want to read, and don't want to read, and it gives a little bookshelf of these books, you can review them and see who else is into the same books as yourself)
http://apps.facebook.com/facebookshelf/people/sidebar
Where am I?
(Shows a mini-map of where you live - many a conversation starter this one - I live near a place called "Snake Valley" hehe) http://apps.facebook.com/geostatus/main.php
Top Groups (Allows you to only show your regular groups on your profile, and people can then "click all" if they want to see all - I love this because then I have a "one-click" access to groups that I own and active groups that I like to check out more)
http://apps.facebook.com/mygroups