Hi Logie,
There's claims that Windows 7 offers better battery life over Vista, so you could try that.
Additionally, have a look at underclocking and (especially) undervolting your CPU.
There is a also minor battery life boost to be had if you use a lower RPM rated hard drive.
Lastly, depending on what video card you have, you could try to underclock/undervolt your video card.
I'm sure there's heaps of other things you could try, but these are the ones I know of off the top of my head
