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.
popsy pops poops popes poppas popsie peps pups poppies paps pips pupas pipes peeps papas pepos pupus pappus papacy papaws papoose pappies pappose pappous pawpaws puppies pappoose
popsy biopsy ops topos whoops dopes topes soaps soups opus lops roups gipsy coops chops oops opes knops loops mopes goops coups copse cops copes woops poesy mops fops loups hopes kops gypsy ropes popes hops pops poops hoops posy bops lopes hyssops sops dopas tipsy topis tops whops wops shops
pop poop pope poppa poppy epopee epopoeia