If you hae upgraded your operating system to iOS 4.2.1, which is the latest you can get on the 3g, then you are stuffed when it comes to apps! Facebook doesn't work, neither does Kindle. The only workaround apart from jail breaking the phone is to add a shortcut to Facebook via Safari, to your home screen, it is the mobile version but better than nothing and it has the 'F' icon so it's easy to find.
