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.
preppy prepay prep preppie preop perp prop priapi hyperope
preppy repay repp crappy creepy crepey crepy grippy prepay drippy trippy
pare pree repro repair reaper pareu pere perea pereia pore pareo pure prey puree pyre peeper pepper peppery peppier reappear repour spree