TLP utility, which implements a sane default configuration file which should enable some improvement right out of the box.
From the docs:
TLP saves laptop battery power on Linux without the need to understand every technical detail. TLP comes with a default configuration already optimized for battery life, so you may just install and forget it. Nevertheless TLP is highly customizable to fulfil your specific requirements.
Visit the installation docs for info on how to install on common linux distros, and to find information on configuration.
It appears there are some additional capabilities/features available for users with IBM/Lenovo ThinkPads.
For non-thinkpad machines running a flavor of Ubuntu install with:
sudo apt-get install tlp tlp-rdw
Start the utility:
sudo tlp start
Check battery status:
``` sudo tlp-stat -b