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.
nipas nips napas nappas naps knaps knops napes neaps neeps nappes nappies
nipas pas huppahs gips gipsy capias copays cowpeas hips cuppas kappas koppas quipus bypass opahs papaws pupas pips repays rips sepias sips spas zips dipso tapas tipis tipsy whips chips chuppas yipes pawpaws lips pase poppas pays paws pass kapas kips quips peas lipase mips nappas pias napas nips papas pipes paps repass ripes rupiahs sipes spaes spays dips dopas tepas tips upas wipes chuppahs ships yips
nipa nip napa nippy snip snipe snippy