Don't get caught without power again. Keep an extra AC adapter in your notebook bag. That way it's always there and you don't have to remember to unplug the one from your desk before going somewhere.
This great accessory works with ThinkPad Z60t and Z60m Series notebooks, as well as the ThinkPad Advanced Mini Dock, ThinkPad Essential Port Replicator, and the ThinkPad External Battery Charger.