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.
whittret waitered watered
whittret tret treat attrit outtrot retreat street
whitter whetter whiter whitier wittier twitter twittery