stole a better duplicate-line function from the internet

helpers.el

@@ -29,13 +29,26 @@
 ;; Duplicate Line
 ;;
 
-(defun duplicate-line()
-  (interactive)
-  (move-beginning-of-line 1)
-  (kill-line)
-  (yank)
-  (newline)
-  (yank))
+;; From: http://tuxicity.se/emacs/elisp/2010/03/11/duplicate-current-line-or-region-in-emacs.html
+(defun duplicate-current-line-or-region (arg)
+  "Duplicates the current line or region ARG times.
+If there's no region, the current line will be duplicated. However, if
+there's a region, all lines that region covers will be duplicated."
+  (interactive "p")
+  (let (beg end (origin (point)))
+    (if (and mark-active (> (point) (mark)))
+        (exchange-point-and-mark))
+    (setq beg (line-beginning-position))
+    (if mark-active
+        (exchange-point-and-mark))
+    (setq end (line-end-position))
+    (let ((region (buffer-substring-no-properties beg end)))
+      (dotimes (i arg)
+        (goto-char end)
+        (newline)
+        (insert region)
+        (setq end (point)))
+      (goto-char (+ origin (* (length region) arg) arg)))))
 
 
 ;;

keybindings.el

@@ -62,7 +62,7 @@
   (global-set-key (kbd "M-n") 'textmate-column-down))
 
 ;; Duplicate line (via helpers.el)
-(global-set-key (kbd "C-x C-d") 'duplicate-line)
+(global-set-key (kbd "C-x C-d") 'duplicate-current-line-or-region)
 
 ;; Align to equal signs
 (global-set-key (kbd "C-x a =") 'align-to-equals)