I am looking to be able to share my Mobile Internet Connection across my LAN.

My current set up is a MacBook Pro (Leopard) that connects to the internet through a mobile dongle provided by my phone service provider (vodaphone), which then connects via ethernet to a router (Apple Airport Extreme). I then hope to be able to use that internet connection with the other devices connect to the LAN, such as a work laptop (Vista), Apple TV and XBox 360.

I am not sure what I need to do in order to achieve this,

Any help would be hugely appreciated.