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.
ritard retard retired retread reiterate reuttered retort redried retreat retried
leotard petard ritard retard dotard tart tetrad tardo start tared nitrid trod putrid turd teared dared hatred hotrod metred mitred stared tardy trad chytrid
rioter ritter rotary writer fritter criteria critter crittur gritter grittier triter