If you're interested in picking a passphrase using the Diceware method but don't want to bother with compiling a program for what is most likely a one-off use, you're in luck. Dr. Drang over at And now it’s all this shows how to use a simple pipeline to get random words from the Diceware list.
He even shows you how to build your own lists using books from Project Gutenberg. If you're on OS X, you won't have
shuf available so you'll have to install the GNU Coreutils but this is easily done via Homebrew if you don't like compiling your own utilities.
This is a nice solution and easier than bringing up my Lisp environment for those rare occasions when I want a passphrase.