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.
poop pop pope poppy poppa pip pup pap pep pipe pepo pupa pipy peep papa pupu papaw pappi pappy peppy pupae puppy
hoop coop goop loop poop whoop op