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.
cupid copied couped cupped caped coped capita capped cooped copped quipped
cupid lipid updo duped souped pied vapid jauped copied couped paid lipoid lipide louped poppied rapid repaid rouped sapid spied tepid yauped
cup coup coupe cuppa cuppy scup