This video is an "oldie" but a "goodie."
piece /pees/ (long "e" sound) versus piss /pis/ (short "i" sound)
fork /fork/ ("or" sound) versus fuck /fuk/ (short "u" sound)
sheet /sheet/ (long e sound) versus shit /shit/ (short i sound)
peace /pees/ (long "e" sound) versus piss /pis/ (short "i" sound)