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.
cupel couple cupola cupula cupule cupulae copal copula copulae
cupel lapel chapel duple spell peel pele appeal appel couple peal pupil pupal rappel repeal repel ripely speel speil spiel tupelo shapely
cup cape cope coup coupe cuppa cuppy scup