/Users/<YourUser>/Library/Caches/com.apple.dt.Xcode. I wouldn't usually mess with this sort of internal caches, but in this case it looks like XCode won't remove old files after installing new ones: I had three .dmg files with different versions of Cli-Tools. I removed all .dmg files except latest version, and it doesn't look like I broke anything, so it's probably a safe trick. In my case, I claimed back some 250 MB -- not huge, but coupled with cleaning all caches for my secondary browsers (done from the proper UI), I got back about 1.5 GB today.
04 March 2013
Clean your Xcode downloads folder to reclaim some memory
I'm always looking for ways to reclaim space on my crammed hard disk. Thanks to the lovely JDiskReport, I've found a little directory where XCode stores the files it downloads when you choose to install components from the Preferences screen: