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.
haddest hadst headiest headset headstay hoodiest hideosity haughtiest hottest hootiest
haddest baddest saddest reddest maddest oddest weediest neediest deist moodiest seediest beadiest dowdiest giddiest loudest muddiest deediest readiest faddist tidiest widest shadiest fideist woodiest headiest rudest didst lewdest nudest gaudiest ruddiest podesta deadest rowdiest reediest hoodiest modest doest leadiest modesty bawdiest faddiest shoddiest