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.
sepias spas spies spays seeps sepoys speiss saps sips zeps ceps sups spaz sops seapiece spues soaps spicy spice spews sipes cepes spazz soups spacy supes spaes specie spicey hyssops
pias sepias capias pas pis pass paws kapas piss nappies papaws pays pase paps pips piso nappas nipas papas puppies pappies tawpies yippies chuppahs cheapies whoopies upas tipis tapas poppies spies spas lipase napas repays cowpeas kepis opahs copies copays buppies kewpies pois kappas bypass guppies lapis cowpies rupiahs huppahs cuppas koppies hippies repass peas koppas pies pawpaws poppas pupas spaes spays dopas tapis tepas topis weepies chappies chippies chuppas yuppies