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.
preppies preps preops prepays prepuce pyropes perps props hyperopes hyperopias priapus
crappies croppies preppies rappees frappes harpies creepies grippes groupies sharpies
preppie preppy prep preop prepay