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.
ripeness ripens ripienos ropiness rapines reopens repines repins
ripeness hippieness cheapness dopiness dippiness soppiness sappiness penes peones happiness hipness hippiness lippiness mopiness loopiness nappiness nippiness openness peppiness pipiness ropiness soapiness deepness dopeyness weepiness choppiness