Emacs ships with a lisp-mode for Common Lisp that supports basic stuff like indentation, S-expression navigation and font-locking.
If you're doing serious Common Lisp development you should have a look at the complementary SLIME, which gives you the ability to develop Lisp programs interactively. Here's a few useful Emacs Lisp code snippets for your SLIME configuration within your Emacs configuration file:
;; a list of alternative Common Lisp implementations that can be ;; used with SLIME. Note that their presence render ;; inferior-lisp-program useless. This variable holds a list of ;; programs and if you invoke SLIME with any prefix argument, ;; like M-- M-x slime or C-u M-x slime, you can select a program ;; from that list. (setq slime-lisp-implementations '((ccl ("ccl")) (clisp ("clisp" "-q")) (cmucl ("cmucl" "-quiet")) (sbcl ("sbcl" "--noinform") :coding-system utf-8-unix))) ;; select the default value from slime-lisp-implementations (if (eq system-type 'darwin) ;; default to Clozure CL on OS X (setq slime-default-lisp 'ccl) ;; default to SBCL on Linux and Windows (setq slime-default-lisp 'sbcl)) (add-hook 'lisp-mode-hook (lambda () (run-hooks 'prelude-lisp-coding-hook))) (add-hook 'slime-repl-mode-hook (lambda () (run-hooks 'prelude-interactive-lisp-coding-hook))) ;; start slime automatically when we open a lisp file (defun prelude-start-slime () (unless (slime-connected-p) (save-excursion (slime)))) (add-hook 'slime-mode-hook 'prelude-start-slime) ;; Stop SLIME's REPL from grabbing DEL, ;; which is annoying when backspacing over a '(' (defun prelude-override-slime-repl-bindings-with-paredit () (define-key slime-repl-mode-map (read-kbd-macro paredit-backward-delete-key) nil)) (add-hook 'slime-repl-mode-hook 'prelude-override-slime-repl-bindings-with-paredit) (eval-after-load "slime" '(progn (setq slime-complete-symbol-function 'slime-fuzzy-complete-symbol slime-fuzzy-completion-in-place t slime-enable-evaluate-in-emacs t slime-autodoc-use-multiline-p t) (define-key slime-mode-map (kbd "TAB") 'slime-indent-and-complete-symbol) (define-key slime-mode-map (kbd "C-c i") 'slime-inspect) (define-key slime-mode-map (kbd "C-c C-s") 'slime-selector)))