Facebook app for iPhone has been updated (v3.4.1) with phone number support. The app now lets you find friends via their phone number.
Facebook for iPhone makes it easy to stay connected and share information with friends. Use your iPhone to start a conversation with Facebook Chat, check your friends’ latest photos and status updates, look up a phone number, or upload your own mobile photos to Facebook while on the go.
When you are in the app, tap on your own profile and it will prompt you a message to ask if you want to let your friends call you using your phone number.
Friend list now has the ‘phone’ icon.
You can get the Facebook app for FREE on the AppStore.