I just came across the Anything extension for Emacs. After you load anything.el, you can type M-x anything RET and a substring of, well, anything. Looks like a handy shortcut. It’s like Quicksilver, but for Emacs. Grab anything-config.el for a bunch of useful functions.

Here’s my current configuration:

(require 'anything)
(require 'anything-config)
(setq anything-sources
      (list anything-c-source-buffers
            anything-c-source-file-name-history
            anything-c-source-info-pages
            anything-c-source-man-pages
	    anything-c-source-file-cache
            anything-c-source-emacs-commands))
(global-set-key (kbd "M-X") 'anything)