Q:

How can I map the "Archived" folder to "All Mail"? 

I would like to map the "Archived" folder that's created when you Archive mail to the "All Mail" folder in my Gmail account.   How can I do this? 

A:

For some reason stackexchange isn't letting me comment on the approved answer. 
In any case, jtbandes' comment is incomplete, you have to set the custom app shortcut as:
"Message>Move To>All Mail"
Note the lack of spaces between the words.  This is critical; it won't work otherwise.  Simply typing "All Mail" will trigger multiple, redundantly named menu items with the keyboard shortcut.  
I've assigned mine to Command-Y to approximate the Gmail shortcut. 
I learned this from a comment by LaraCroft_NYC at https://discussions.apple.com/thread/2572960?start=0&tstart=0

A:

You can't do this in Lion.  File a bug if you want to be able to do this.