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.
cost coast costa coset cosset costae cast coesite caste cosied cuesta casita casette gooiest cassata caseate cassette gast gust kist cased guest gusto gusty quest
boost ghost host cost lost most post roost dost tost wost