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.
sups soups supes saps spas sips sops suppose sipes spues soaps spays seeps spies spews spaes sepias spouse speise sepoys speiss hyssops ceps spaz zaps zeps zips space spacy spazz spice spicy
jaups coups cups loups pups roups soups sups dups tups ups whaups whups yaups yups