AX Developer Center on MSDN has been live for a while now.

We have added a few redirects to make the site more accessible:

http://msdn.com/ax 

http://msdn.com/axapta

http://msdn.com/dynamicsAx

http://msdn.com/dynamics/ax

If you are looking for developer documentation on AX and haven't visited this site yet, you are doing a disservice to yourself!