On Monday, MCE announced a Dual Battery Charger for the new iBook (Dual USB). The charger is said to ship in mid-February.
This is a very useful product if you will be away from an electrical power outlet for longer than the life of your single battery. The only inconvenience is that, unlike the PowerBooks, the iBook does not allow hotswapping of batteries during sleep. You have to shut down your system, swap the battery, and start up again every time.