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.
pupil pupal peppily papilla papillae papal pepla pipal papula papule peepul people popple papally papulae
pupil couple uppile dopily spill spiel spail sappily ropily pupal peppily nippily loopily cupel huipil pail happily pily pill pili pile pial roupily soapily speil spile spoil duple choppily