There are many Apps available for assisting and managing batter life on the iPhone and iPod Touch. The fact of the matter is that these devices do a lot in the course of a day so couple that with the fact that very little in the way of battery technology has evolved ( without increasing the size and weight of these devices exponentially) so the result is a short battery life. There are things we can do to eke out a bit more use time.
My favorite App for managing the battery is Battery Dr. Pro (this link will open iTunes iStore to the product page where you can download the app from there).
The key thing to know about extending the battery life on the iPhone is first and foremost USING the battery; it’s OK to let it run down. That said you also want to make sure you have enough sources for charging. You need several cables, a wall adapter, a car adapter (all of these can be USB based) and you can always plug your iPhone into any PC’s USB port to get an extra charge (just DON’T allow it to incorporate itself into another person’s iTunes except for the one on your own computer!)
Additionally turning off unnecessary service is always good too. You can turn off WiFi if you just want to listen to the iPod, play games or read books from the pre-installed apps. If you have no Bluetooth devices make sure Bluetooth is turned off. Setting it to Airplane mode can really extend the battery, it also turns off the phone and Wi-Fi automatically so be prepared for some well-deserved quiet time.
Please let me know if you have further questions or interests. Enjoy!