iPhone-Codes has a great write up on some iPhone battery saving tips that may help a lot of users.

Change Mail Auto-Check: Turn off Mail auto-check or increase the auto-check interval. To turn off auto-check, from the Home screen choose Settings > Mail > Auto-Check and tap Manual. To increase the auto-check interval, go to Settings > Mail > Auto-Check and tap Every hour. Note that this is a global setting that applies to all active mail accounts on your iPhone except push mail accounts with push mail enabled.

Turn off Push Mail: If you have a push mail account, turn off push mail when you don’t need it. Go to Settings > Mail, choose the push mail account, tap Advanced, and set Use Push Mail to Off. Messages sent to this account will now be received on your phone based on the global Auto-Check setting rather than as they arrive.

Auto-check fewer Mail Accounts: You can save power by checking fewer mail accounts. This can be accomplished by turning off a mail account or by deleting it. To turn off a mail account, go to Settings > Mail, choose a mail account and set Account to Off. To remove an account, go to Settings > Mail, choose a mail account and tap Delete Account.

Turn off Wi-Fi: If you rarely use Wi-Fi, you can turn it off to save power. Go to Settings > Wi-Fi and set Wi-Fi to Off. Note that if you frequently use your iPhone to browse the Web, battery life may be improved using Wi-Fi instead of EDGE.

Turn off Bluetooth: If you rarely use a Bluetooth headset or car kit, you can turn off Bluetooth to save power. Go to Settings > General > Bluetooth and set Bluetooth to Off.

Adjust Brightness: Dimming your phone’s screen is another way to extend battery life. Go to Settings > Brightness and drag the slider to the left to lower the default screen brightness. Additionally, turning on Auto-Brightness allows your phone’s screen to adjust its brightness based on current lighting conditions. Go to Settings > Brightness and set Auto-Brightness to On.

Turn off EQ: Applying an equalizer setting to song playback on your iPhone can decrease battery life. To turn EQ off, go to Settings > iPod > EQ and tap Off. Note that if you’ve added EQ to songs directly in iTunes, you’ll need to set EQ on iPhone to “Flat” in order to have the same effect as “Off” because iPhone keeps your iTunes settings intact. Go to Settings > iPod > EQ and tap Flat.

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