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.
sixty sixte sext sagacity zygosity sexto sequacity sickest saggiest soggiest suckiest
sixty gaseity zygosity sixte sequacity sagacity rugosity mucosity mixt megacity laxity fixit jocosity haecceity fugacity fixt fixity loquacity dixit