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.
soups sups sops soaps supes spouse saps suppose hyssops spas sips seeps spews sipes spies spues spays spaes sepias sepoys speise speiss ceps spaz zaps zeps zips
loups soups roups coups ups ops popes cops opus copes coupes pupus coops loupes coypous lupous ropes biopsy quips lupus copious soaps mopes tops yaups chops knops hoops pious goops topis lopes taupes dupes dopas supes mops opes hopes poops pappous oops cups jupes pops upas whops hops loops copse pups jaups lops pupas popsy whaups woops bops hyssops sops spouse sups dopes dups topes topos tups fops kops whoops whups wops shops yups
soup soupy sop sup soap soapy soppy supe