Something

;; Put backup files (ie foo~) in one place too. (The backup-directory-alist                                                     
;; list contains regexp=>directory mappings; filenames matching a regexp are                                                    
;; backed up in the corresponding directory. Emacs will mkdir it if necessary.)                                                 
(defvar backup-dir (concat "/tmp/emacs_backups/" (user-login-name) "/"))
(setq backup-directory-alist (list (cons "." backup-dir)))