Quick virtualenv fix on Mountain Lion
It appears that Apple somehow broke Python in Mountain Lion, so even with the latest Command Line Tools and Xcode 4.4 virtualenv won't properly work. During virtual environment creation it will try to install easy_install inside /Library hierarchy. So let's give it a quick workaround. Let's install custom python into your $HOME-directory using pythonbrew!
Installing proper Command Line Tools
Without the Apple Mac Developer account you won't even see the proper download link for the latest CL Tools and the old one won't work on ML. So here's the link: http://goo.gl/iBTXh. It points towards the Apple website so don't worry.