IOS 5 has officially been released and is available to download from the following links:
iPhone 4S - Download
iPhone 4
GSM - Download
CDMA - Download
iPhone 3GS - Download
iPad 2
WiFi - Download
GSM - Download
CDMA - Download
iPad - Download
iPod Touch 4G - Download
iPod Touch 3G - Download
The new IOS 5 update brings with it the ability to upgrade your firmware over-the-air, meaning you do not need to plug your iDevice into iTunes in order to upgrade it. When a new update is ready your device will download it over WiFi (or 3G).
