Xcode: Delete applications in Organizer/Archives?

In Xcode 4 you can delete an archived application manually. Right click on it, Show in Finder, remove it as any other folder. Xcode will detect the deletion and update the list of archived apps.

Archives are just bundles with .xcarchive extension under ${HOME}/Library/Developer/Xcode/Archives. They are organized in folders by date (like 2011-11-11). You can look inside using Show Package Contents menu item, like any other bundle.

XCode 8

You need to clear out this folder. It is where Xcode app archives are stored.

${HOME}/Library/Developer/Xcode/Archives

It will also save space on your hard drive. I found that I had upwards of 200 GB of app archives lol.