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.
loopiness lippiness lupines lapins lipins lupins lippens
happiness lippiness dippiness pipiness loopiness sappiness weepiness peppiness soapiness mopiness nappiness hippiness soppiness choppiness dopiness nippiness ropiness pines rapines chopines deepness ripeness lupines opines repines hippieness supines cheapness spines hipness pins