According to the manual node on Filling, several of the fill functions take an optional JUSTIFY argument that you can use. So, for example, to fill a paragraph with right justification, you can use (fill-paragraph 'right).
You can also use (justify-current-line 'right) for a single line.
If you plan to use these options a lot, you could wrap them in functions, such as the following, and then bind these functions to the keys of your choice:
(defun right-justify-current-line ()
"Right-justify this line."
(interactive)
(justify-current-line 'right))
(defun right-fill-paragraph ()
"Fill paragraph with right justification."
(interactive)
(fill-paragraph 'right))
Here's a function you might drop in as a replacement for fill-paragraph. With various prefixes, it allows you to decide what kind of justification to use on the paragraph you're filling:
(defun fill-paragraph-dwim (&optional arg)
"Fills the paragraph as normal with no prefix. With C-u,
right-justify. With C-u C-u, center-justify. With C-u C-u C-u,
full-justify."
(interactive "p")
(fill-paragraph (cond ((= arg 4) 'right)
((= arg 16) 'center)
((= arg 64) 'full))))
If you don't want to fill when you're right-aligning, you can use the following function, which is cribbed directly from the center-region function with a single-line change to make it align right instead:
(defun right-region (from to)
"Right-justify each nonblank line starting in the region."
(interactive "r")
(if (> from to)
(let ((tem to))
(setq to from from tem)))
(save-excursion
(save-restriction
(narrow-to-region from to)
(goto-char from)
(while (not (eobp))
(or (save-excursion (skip-chars-forward " \t") (eolp))
;; (center-line)) ; this was the original code
(justify-current-line 'right)) ; this is the new code
(forward-line 1)))))
