Speaking of batteries, coconutBattery is a donationware utility that shows Mac laptop users the current charge of their battery – and its current maximum capacity of it in relation to its original capacity. In addition, it reports on the battery-loadcycles (how often did you fully load your battery), on the current charger (it will warn you if the wrong type of charger is being used) and last but not least information about the age of your Mac. coconutBattery is Universal Binary, so will run on PPC and Intel Macs.
(David Alison's Blog) | Cost: Free (donations welcome) | Requires: Mac OS X 10.4+ | For further info...