Looks like there is only information about Xcode 4 on Apple's developer site http://developer.apple.com/xcode/index.php. What's more, Xcode 4 is not free -- you need to sign up for one of the developer programs, or alternatively buy it at the Mac App Store for the outrageous sum of €3.99 (or you local equivalent).
I am cheap bastard. This whole blog is about running OS X cheap after all. Well, actually I would have spent the money, but Apple's credit card verification drives me crazy. Ever tried using a credit card issued in a country different from the store's country? I got an error message saying "this card is not valid in the Netherlands". This is nonsense of course, every other shop happily accepts it. I digress.
So, where do I get Xcode 3 from? Turns out that it's still available from the old developer's site at http://connect.apple.com. Log in with your Apple id, select "Developer Tools".