Apple has just released iOS 4.3.1 update for iPhone 4, iPhone 3GS, iPad 2, iPad, and iPod touch 4G/3G. This is just a minor update to fix bugs, vulnerabilities and battery life woes on all iOS devices.
To update to iOS 4.3.1, all you need to do is to connect your iPhone, iPad or iPod touch with your computer via USB and start iTunes 10.2.1. You should now see a message as shown below, simply click on “Download and Install” (Mac OS X) or “Download and Update” (Windows) button to get on to the new firmware.
Direct Download Links for iOS 4.3.1 (Official from Apple)