Random, memorable, crack-resistant phrases drawn from a 512-word diceware-style list. Tune length, separators and case — with live entropy.
Length beats complexity. A passphrase of 5 words from this 512-word list gives 45 bits of entropy; 6 words give 54 bits — comparable to a random 9–11 character password, but vastly easier to type and remember. Add digits to each word for another 3.3 bits per word. The classic xkcd comic made this famous: "correct horse battery staple" — four ordinary words that take a supercomputer centuries to crack.