Certain sites like Newegg and others like it employ a drill down category selection that may help you. You can sort by one factor at a time or multiple factors with power search to do it all at once. Each successive filter applied will limit the possible categories to choose from.
After you get a short list, I would highly recommend researching it online through and reading as many reviews as possible.
However, if you can afford it, and are fine with a more industrious look rather than something flashy, I'd recommend looking at Lenovo's T series.
Edit: more info below
I think I saw this once a while ago, but I can't remember what it is. Perhaps try http://www.notebookreview.com/.
Generally, the following things will use more power and shorten battery life:
- Dedicated/discrete graphics card
- Larger screens
- Faster hard drives (7200 vs 5400, very marginal though - power shouldn't be the concern in choosing between these)
- Multiple hard drives
- Using your CD/DVD/Blue-Ray drive
- CCFL LCD backlights (vs LED)
Also, generally, bigger batteries with more cells will last longer than shorter batteries with less cells. However, you can't compare a 13" - 3 [battery] cell laptop to a 17" - 9 cell laptop.
Furthermore, remember that manufactures will overstate their battery life and show it under the best conditions (low LCD display, lowering processor to barely usable, turning off discrete graphics cards, turning off wireless networking).
