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.
swotter swatter sweater sweeter seawater sweatier
swotter watter wetter whetter whitter wittier swatter twitter twittery