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:
(global-set-key (kbd "M-X") 'anything)