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.
opahs ops oops opes opus oppose
opahs huppahs chuppahs pas spas sepias cowpeas repays copays pias pupas capias pawpaws tepas lipase bypass kappas kapas dopas pays papaws paws nappas cuppas nipas spaes rupiahs repass poppas paps napas papas pehs koppas pase pass peas spays tapas upas chuppas