http://developer.apple.com/ios/download.action?path=/ios/ios_sdk_4.0.1__final/xcode_3.2.3_and_ios_sdk_4.0.1.dmg

Xcode 3.2.3 and iOS SDK 4.0.2 for Snow Leopard (10.6.4)

http://developer.apple.com/ios/download.action?path=/ios/ios_sdk_4.0.2__final/xcode_3.2.3_and_ios_sdk_4.0.2.dmg

Xcode 3.2.4 and iOS SDK 4.1 for Snow Leopard (10.6.4)

http://developer.apple.com/ios/download.action?path=/ios/ios_sdk_4.1__final/xcode_3.2.4_and_ios_sdk_4.1.dmg

Xcode 3.2.5 and iOS SDK 4.2 GM for Snow Leopard (10.6.4)

http://developer.apple.com/ios/download.action?path=/ios/ios_sdk_4.2_gm_seed/xcode_3.2.5_and_ios_sdk_4.2_gm_seed.dmg

Xcode 3.2.5 and iOS SDK 4.2 for Snow Leopard (10.6.4)

http://developer.apple.com/ios/download.action?path=/ios/ios_sdk_4.2__final/xcode_3.2.5_and_ios_sdk_4.2_final.dmg

Xcode 3.2.6 and iOS SDK 4.3 GM Seed for Snow Leopard (10.6.6)

http://developer.apple.com/devcenter/download.action?path=/ios/ios_sdk_4.3_gm_seed/xcode_3.2.6_and_ios_sdk_4.3_gm_seed.dmg

Xcode 3.2.6 and iOS SDK 4.3 for Snow Leopard (10.6.6)

http://adcdownload.apple.com/Developer_Tools/xcode_3.2.6_and_ios_sdk_4.3__final/xcode_3.2.6_and_ios_sdk_4.3__final.dmg

Xcode 3.2.6 and iOS SDK 4.3.1 for Snow Leopard (10.6.6)

http://adcdownload.apple.com/Developer_Tools/xcode_3.2.6_and_ios_sdk_4.3__final/xcode_3.2.6_and_ios_sdk_4.3.dmg

Xcode 4 and iOS SDK 4.3 for Snow Leopard (10.6.6)

http://developer.apple.com/devcenter/download.action?path=/Developer_Tools/xcode_4_and_ios_sdk_4.3__final/xcode_4_and_ios_sdk_4.3__final.dmg

Xcode 4.0.1 and iOS SDK 4.3.1 for Snow Leopard (10.6.6)

http://developer.apple.com/devcenter/download.action?path=/Developer_Tools/xcode_4.0.1_and_ios_sdk_4.3/xcode_4.0.1_and_ios_sdk_4.3.dmg

Xcode 4.0.2 and iOS SDK 4.3.2 for Snow Leopard (10.6.6)

http://developer.apple.com/devcenter/download.action?path=/Developer_Tools/xcode_4.0.2_and_ios_sdk_4.3/xcode_4.0.2_and_ios_sdk_4.3.dmg

Xcode 4.1 SDK5.0 for Snow Leopard  (10.6.7)

Xcode 4.1 SDK5.0 for Lion (10.7)

Xcode 4.1.1 SDK5.0 for Lion (10.7)

Xcode 4.2 and iOS SDK 5.0 for Snow Leopard (10.6.7)

https://developer.apple.com/devcenter/download.action?path=/Developer_Tools/xcode_4.2_with_ios_5_sdk/xcode_4.2_and_ios_5_sdk_for_snow_leopard.dmg

Xcode 4.2 and iOS SDK 5.0 for Lion (10.7)

http://developer.apple.com/devcenter/download.action?path=/Developer_Tools/xcode_4.2_with_ios_5_sdk/xcode_4.2_and_ios_5_sdk_for_lion.dmg

Xcode 4.2.1 and iOS SDK 5.0 for Lion (10.7)

Xcode 4.3.2 and iOS SDK 5.1 for Lion (10.7)

Xcode 4.4  and iOS SDK 5.1 for Mountain Lion