We are already discussing monitors that allow for proper anamorphic monitoring here: http://www.eoshd.com/comments/topic/1832-monitors-for-2x-and-15x-stretch-preview/
But I thought that it would be useful to have one thread where we all share our Custom Scale settings for anamorphic monitoring (especially since Magic Lantern has brought back 4:3 shooting in raw mode at assorted resolutions).
For those unfamiliar with this feature, the best description that I have found is in the manual for the old DP1: http://www.eoshd.com/comments/uploads/gallery/album_14/gallery_18451_14_22383.png