I've taken a list of English words, and examined each of them to see what they sound like (using the PHP metaphone function). This page lists the most common metaphone codes, along with their words. You can also search for a word of your own, and see which words sound similar - and which ones rhyme, and which ones alliterate.
couple cupule copulae cupulae copal cupel copula cupola cupula
couple duple diploe plie dipole dapple supple spale plew papule pupil nipple maple pele pile plea tipple uppile popple pole zeppole cupule pule fipple hopple copulae cupel cupulae apple maypole papulae people pupal ripple spile pale topple wheeple
coup coupe cop cup coypu scope scop cuppy cuppa cowpea coypou cowpie copy cope copay coop scup