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.
poppy puppy poppa pappy peppy pop pipy poop pope pappi pup pap pep pip papa peep pepo pipe pupa pupu
loppy poppy hoppy choppy soppy lippy dopey zippy soupy sappy koppa soapy ropey guppy goopy tippy nappy gappy mopey loopy chippy shoppe pipy poppa ropy dopy peppy dippy zappy copay puppy pappy whippy nippy roupy copy mopy buppy happy hippy cuppy quippy yuppy
poppa poppy pop hoppy koppa koppie loppy pappi pappy peppy poop pope puppy soppy