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.
copious coypous coypus copies cops cowpies copes copse coups coops coupes capias copays cowpeas koppies coppice caps cups kops capes capiz capos goops kepis cuppas koppas quipus guppies kewpies quippus
pious copious coypous lupous pappous spouse pis pus