Ever since reading that xkcd comic and learning about diceware, I've really wanted to create a password generator that could spin out complete diceware sentence

Ever since reading that xkcd comic and learning about diceware, I've really wanted to create a password generator that could spin out complete diceware sentences of arbitrary length. (Markov chains?) Mnemonics of various kinds could be taken into consideration: rhymes, onomatopoeia, etc. Instead of a 4-word nonsense passphrase, you'd get something like "the red rancid raccoon bit into the butter bucket biscuit" — easy to remember and secure. Unfortunately, I'm not too familiar with this subset of programming. (Limiting the word pool of each slot due to mnemonics would complicate the entropy calculation, but it should still be fairly straightforward.)