Which iOS devices do not support iOS 5? What is the complete list of iOS devices (iPod Touch, iPhone, iPad) that are unable to update to iOS 5.0?
Devices not supported by iOS 5:


iPhone (original)
iPhone 3G
iPod Touch first generation
iPod Touch second generation
AppleTV


Source: http://www.apple.com/ios/features.html . "iOS 5 is compatible with: iPhone 3GS, iPhone 4, iPhone 4S, iPod Touch 3rd generation, iPod Touch 4th generation, iPad, iPad 2."