In Tiger, there's a new option for extending your laptop's battery life. You can tell Tiger to automatically dim your display when the laptop's drawing from battery power. Just pop over to the "Energy Saver" prefs pane, choose Settings for: Battery, click Show Details, and select the Options pane. Finally, check the "Reduce the brightness of the built-in display when using this power source" checkbox.
Additionally, the pmset command-line utility has gained some new abilities. One of the nicest, in my opinion, is a simple way to find out if your machine is on battery or AC power:
$ pmset -g ps
Currenty drawing from 'AC Power'
-InternalBattery-0 96%; AC attached; not charging
This can be a very handy thing to examine when setting up periodic scripts that are power-hungry -- you want to be sure that they won't start in the middle of that trans-Atlantic flight.

