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.
rappini rapini rapine rappen ripieni repin repine ripieno ripen reopen repugn
rappini pippin rapini ripieni cioppino doupioni douppioni pin
rappee frappe crappie crappy grappa rap