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.
pupas pups pupus papas poppas paps pips peps pops puppies peeps popes popsy poops pipes pepos popsie papaws pappus papoose pappies pappose pappous pawpaws poppies pappoose
pupas upas ups pas kapas nappas cups cowpeas kappas huppahs coupes coups copays capias papaws koppas pawpaws pupus jaups repays sepias spaes spays sups dupes tapas tepas jupes whaups chuppahs yaups bypass opahs loupes quips lupus poppas pias peas pays pass paws papas cuppas pase lipase loups nipas pups paps repass roups soups spas supes dopas dups taupes tups napas whups chuppas yups