Here's a command, based on @itsjeyd's answer, that is robust to the edge case listed in the comment to that answer (that is, when you're on the last heading/subtree):
(defun org-end-of-subtree ()
(interactive)
(let ((org-special-ctrl-a/e t))
(if (condition-case nil
(outline-forward-same-level 1)
(error t))
(progn
(goto-char (point-max))
(outline-back-to-heading))
(outline-previous-visible-heading 1))
(org-end-of-line 1)))
