If you want to get more battery life from your mac I highly recommend grabbing TurboBoost Switcher for Mac OS X. This little menu bar utility helps you control the turbo boost capability of your CPU to help conserve battery, minimize heat and almost completely reduce fan noise whenever you want.
I have mine setup to turn off the Intel Turbo Boost when unplugged and I am seeing huge increases in battery life. This does come at the expense of performance but when I am away from a charger my workloads tend to be lighter and I have not noticed a big difference.
I really hope Apple builds something like this into their next OS because they are dramatically changing how kernel extensions and drivers work in future releases and I think this tool might end up not working anymore.