http://diceware.katmatfield.com
This is a simple app to generate passphrases using the Diceware technique.
Diceware is a method of generating secure passphrases using, unsurprisingly, dice.
In this method, each word in the passphrase is generated through five dice rolls. The results of the rolls are concatenated to give a five-digit number, which corresponds to a word in the wordlist. Repeat this process seven times to get a passphrase. (Why seven times?).
I made this online version because the other recommended 'short cut' wasn't very short:
If you need to make up passphrases often, get a shoe box or a food storage box about the same size. Put five dice in the box, shake them up vigorously -- at least ten hard shakes -- and then tip the box to let all the dice slide down to one edge. Now open the box, read the dice from left to right, or front to back if a few line up. Then just look up the corresponding word list entry. Repeat this process until you have enough words for your passphrase.