One of the important things on using a laptop while travelling is that if you do not optimize your battery usage, it might go out much faster than expected.
Optimizing battery usage means reducing the power consumption by reducing the screen brightness, disabling aero etc. In order to keep track of your battery usage, it is always good to have third party apps which gives more features and also notification on your usage.
Here are some freeware app for Windows which allows you to keep a watch on the battery usage on Windows 7 and other versions.
1. Battery Care : http://goo.gl/WvTv
2. BatteryInfo : http://goo.gl/Oqxok
3. BatteryBar : http://goo.gl/NZ0j
4. AeroFoil : http://goo.gl/QI6V
5. BatteryEater : http://goo.gl/JZCaf
6. Battery Meter : http://goo.gl/xvRTk