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.
coupe coup cope cop cup cowpea cowpie copy coop cape copay cuppy cuppa coypu coypou koppie cap kop capo gape goop quip
loupe coupe ope whoopie roup toupee mope tope mopey dupe pupae dope pope soupy nope rupee rope lope loup coup cope jupe hope hoopoe ropey roupy soup supe dopey taupe topee whoopee shoppe