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.
repugn repin reopen repine ripen rapini rappen rappini ripieni ripieno
oppugn repugn pun puna puny spun
rep reap repay repo repp arepa crepe crepey crepy prep prepay preppie preppy