Recently, I've stumbled across an application in the android market, Juice Devender, that does exactly what it advertises. The application extends battery life through automated micromanaging of peripherals and software. This combined with another application, Juice Plotter, allows one to actually experiment with different battery preservation techniques (or different ROMs for rooted phones) and compare the results.
More specifically, the application behaves much like any other power management software in Linux installations. It controls the frequency scaling of the processor (if the phone is rooted), it controls networking interfaces and screens to help conserve power. All of this functionality can easily be configured and modified for your desired power settings, but the defaults will provide a significant boost to battery life. This is one more useful utility in a long list that allows us to get the most out of our phones.