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.
retard ritard retired retread retried retort reuttered redried retreat reiterate redroot
leotard petard ritard retard dotard tart tetrad tardo start tared nitrid trod putrid turd teared dared hatred hotrod metred mitred stared tardy trad chytrid
reader readier treater prettier retear retire retiree retore retro retry reutter rotary fretter frettier creator creature greater pretor treader ureter